Hello.
As a completely F2P, and noob, I find myself agreeing with most of what Player J is saying.
I heard much the same from my initial clan mates. I felt dispare. My first F2P I had obviously hosed being in too much of a rush... I hit a dead end campaign normal stage 10. I farmed stage 9 and potions until I had a couple 50's my energy was completely gone (and you get a crap ton of energy early off if you use mission and challenge rewards. I did some assentions, and skill books, and progressed a bit more, but then, I hit an even bigger wall soon after on hard stage 4, even with my full team now 4-50's Forget farming anywhere in hard. I was still stuck on early dungeon levels... and forget spider... (I still ignore that B*T*H). Arena was a complete bust.
My personal advice. PATIENCE.
I rolled a new account, and focused my attention on my starter, as was highly recommended by my clan mates. Fortunately this also happened to coincide with the latest back to back champion rush events, and some bonus rewards and energy. Get that starter to 60 as your first priority. Period. The jump from maxing each star level far outweighs the Assent bonus, from what I can tell so far. (I could be wrong, for 5-6 assentions.... not personally there)
Keep up on your missions and challenges for rewards... even those obnoxious win % crap from some stage ones. Dedicate 50 or so energy each day... they will eventually drop. Continue your relentless drive to leveling food (1 and 2 from all those green shard drops), they will eventually become your 3, 4, and finally.... 5 food for your starter.
For my starter, I chose Elhain. She is still my personal favorite, although many will argue Kael for clan boss. I have a couple poison monks from all those greens who seem to serve just as well on easy clan boss, which is all I am concerned with for now. (PATIENCE).
I've focused on only my starter Elhain. Finally got her to 60. I am still using my new player purple vampire reward gear, and two attack 5 star I managed to pick up from the daily battle reward level 16 or so. I not only broke through my previous wall, I shattered the entire damn thing, and was able to solo all the way up to hard level 8, where the force (red champs) gave me a severe beat down. I should note that focusing on my starter, I currently have no 50's. They were all lunch (except Assassin and Crusader). I took my Warpriest, Assassin, and Crusader (all normal campaign rewards) and had easily leveled them to 40s during normal play through and champion challenge. With them still at 40 and in my party, I got past that minor wall, I couldn't pass stage 10 even with party, so settled in farming hard stage 9 for a while. (DO NOT worry if you can't do hard/brutal 12-3 or 12-6 all the time as all the "youtubers" and "influencers" preach. Farm where you can. For me it was normal 9 whatever a for a while. I never ended up farming normal 12-3/6 at all, since I essentially jumped from 9 normal to 9 hard solo. (PATIENCE)
It turns out farming 9 has some other advantages, as well. Warmaiden. She is a F2P arena must. I have collected enough copies of her to finally get the cooldown bonus on her decrease defense buff. Stage 9 also has Berserker. He ended up being a nice little nuker for my arena, even though I knew I would replace him if I ever managed to pull an Aethel, Kael, or someone better. I did luck out and pull Galek yesterday. While not my preferred choice, F2P beggars cannot be choosers. He will fall into place nicely in my arena, clan boss and dungeon teams for now, and I plan on 6ing him if I don't end up with anything better. With his self speed buff, I do prefer him over Berserker... but no skills yet... I may float both around a bit since Beserker is farmable for skill boosts
Overall, while this is completely my personal opinion and subjective. I am completely F2P. I felt hopeless enough to start a second account after I felt that I had wasted my wealth of free energy that new players can amass from mission and challenge rewards. I started over and exercised a bit more patience. I also followed some clan mate advice. My progress has been much more satisfactory than I initially had.
My Elhain is now 6 star and fully booked (fully booking was again clan advice on my starter). I've assended her just 3 times (and once for my Galek) as potions and assention challenge missions have come up. The rest will come later. I see even more mission rewards for all potion levels on the "hard" mission quest chain. DO look ahead at missions, see what may be in store. That greater arcane you need, may be a mission reward just down the road a bit. No need to grind high level dungeons just yet. PATIENCE.
My arena team is shaping up. I took some more clan advice and farmed Spirithost (campaign stage 4). She was a great addition. With her and Warmaiden, I get speed boost and increase attack from Spirit Host, along with (occasional) decrease defense from Warmaiden. I am not sure if unskilled Galek is a good swap for Berserker quite yet, I also just 4 stared him, so need to max level yet. I will obviously need to pry some skill books from my vicelike grip and use them, while praying to the RNG gods. Either way. I have broken into bronze 3 and have pretty much stayed there for the past few days. You may see me in silver soon.
My clan boss team is OK. My two poison monks are both 3 star max level. I just have to deck them out in all HP gear, and keep them alive with Warpriest so that I can use the poison more than once per battle. I got lucky and summoned another poison monk. I fed him for skill up, and the RNG gods were pleased, and rewarded my faith and dedication with the poison cool down, not one of the worthless dagger skill upgrades. I can usually get 1M+ for the max (easy) chest reward with 2 keys, sometimes I need to hang around for another key to polish off a final 20-30K damage for the best chest reward. Generally clan boss rewards even on easy are better than I can reliably farm on dungeons yet.
Dungeons, I still pretty much still avoid, unless I need for mission or challenge rewards. Clan boss rewards although fewer, seem to be of higher quality, compared to what I can farm. One exception is Minotaur. I hit him 3-4 times per day for the weekly dungeon boss challenge, plus some scrolls as a bonus. I don't worry about maxing masteries yet. I found my first 900 gems were a bit more fun to spend on the 11 ancient shard pack. That is where I pulled my Galek. I can solo Minotaur 9 (most people would say big deal.. but I say PATIENCE). So Ehlain is max on the first two rows of masteries from solo runs. With these daily runs I usually can guarantee 9-14 scrolls to any other champ I want to drag along, or even get a few green scrolls for Elhain. The spider queen B*T*H from H*LL can just go F*CK herself. I got stage 1 for the early mission. No way possible for stage 4 and the dungeon challenge, yet. I need to research a proper F2P team for that B*T*H.
My current new player reward gear still seems a bit better than any 3 or most 4 star I can farm yet. It seems I was lucky with RNG gods as my life-steal new player reward set ended up with both crit% and crit damage%, and work very well for my Elhain. So, I won't focus on gear farming quite yet, as much as just food for my next 60 (probably Galek). However, I am watching for all the % stuff as Player J has suggested. His (advanced gearing) advice not yet posted, is probably (in my opinion) to simply, upgrade some grey gear to level 4 and greens to level 8. Look at the new secondary stat that appears. I aim for all percents, and toss the static scores, except speed which is always static. SPEED IS ALWAYS STATIC. Don't sell speed... almost never if you can afford the space. Every champion benefits from extra speed here and there.
WOW... sorry that got long....
For those TLDR.
PATIENCE. I am completely F2P. I've have just picked up my day 18 ancient shard login reward only today. Following the advice of players like Player J and some clan mates, I have not only broken though my previous brick walls, I've gone and shattered them and flown right by stages on hard that I had initially thought impassable.... only this time I did them completely solo with my starter Elhain, three staring entire stages with glee the entire way, picking up even more bonus rewards.
In my opinion. First, focus primarily on getting your starter to 60 at all costs. Second, focus on mission and challenge rewards rather than dungeons at this point in time. The rewards for these outweigh any of rewards from the dungeon grinding early low level teams can do. Rewards are also super overloaded with bonus energy. Between mission, challenges, daily play time rewards, and the daily battle reward progression, I have yet to spend even a single gem on energy bottles. (Another reason I chose to spurge gems on ancient shards over the mastery scrolls).
Getting to bronze III for mission and arena challenge will probably make you want to smash your head on the keyboard. Go hunt down Spirihost and Warmaiden. Bronze III should in then be within reach, if not already. Silver level... Even I will see on that one. I can breach bronze 4, but then get knocked down to bronze 3 or even sometimes bronze 2...
All in all. PATIENCE. Plan ahead on missions and challenges for spending your energy, versus rewards. Grind your potions when you can win even bigger potion rewards from mission or challenge rewards. Assentions will come with these rewards. Arena, and clan boss will come in time. Gear (lastly in my opinion) will also come in time. Then is truly your time to grind dungeons. "Scratch an itch" if you need to, I absolutely agree. Test how strong you have become with assentions and that rare "good" gear you do stumble on, or upgrade. I still have a personal vendetta with the spider B*T*H, and just have days where I need to see of I can get my revenge. Alas... I still can not complete spider 4 for my dungeon challenge... it will come in time also.
Patience, Have fun and enjoy.