Also, what should I do with my extra rares, because they are making arena hell for me, as I am facing teams with maxed out 6 star legendaries at bronze III.

I can only say, take your time... Because Raid have become a real nightmare for new players.

So if you want to enjoy the game, don't rush it. Build foods using 1* and 2* champs, or maybe extra 3* and 4* if any.

TBH, Jizoh is such an underrated hero, I love that lizard! He's one of the champs that get me to Silver. But I don't do the Speed Nuke team.

That's my best advice, don't rush it, take your time. Or find another game... As I said, this game have turned really unfriendly to new players.

You really don't want to keep any rares that you don't need.  I know that is easier said than done for a new player, but you can use those rares as food to upgrade other champions to 4 star.   You're best bet is to check out a site like AyumiLove to see if the rare is worth keeping, but in general a lot of them are not in the long run.  You will get heaps

I also echo the advice above which is to take your time.  If you hit a brick wall the campaign then run some of the previous stages for the next couple of days while you level up some fodder champions, to then upgrade your main ones.  This isn't really the type of game that you will finish in a month.

Edit: It may also help to show your roster

Don't sacrifice Jizoh at this point, you could still use him in many places. And yes, ranking up commons/uncommons, with the odd duplicate rare here and there, is how everyone gets their 6* champions... though of course, it will go faster and be a bit less grindy once you can farm XP in brutal 12.3. The first 6* is the hardest because you have to farm XP at lower stages so it takes longer. Of course, some of the campaign is harder, for instance because of affinity, so you may need a full team of Galek at 50 and three others at 40 to get through those. Galek at 50 should easily able to farm hard 12.3 once he gets there, though. 

Here is my roster

i

(Update, I purple starred my scrapper to 4 purple * and veteran to 3

Hi! Basically, as other guys have said here, your Galek should be able to beat Hard 12:3 on his own. It might seem counter-intuitive at first, because he might be actually unable to bit on his own some earlier stages of the campaign, like 10 and 11, but that's not because those stages harder; it's just because of the Affinity thing and some specific abilities of enemies there.

So, my piece of advice here - combine whatever the strongest pack you can to get to the Hard 12:3. Then you should be able to farm XP faster. And, indeed, better not to sacrifice Jizon, he's quite a decent Champion

I've got another question; which champion should I use with Galek to beat some campaign levels like Tilshire? I've tried the orc woman (lol) in normal and it succeeded but the problem now is that she's too squishy an gets 3 shot

(Also should I replace Scrapper with veteran???)

You realize that you only need 4 pieces for a lifesteal set, the other two aren't adding any set bonus anymore? Though it's possible that they are the best gear you have, so don't replace any pieces unless you actually have a better alternative. 

Also, you should never be in this position with all your gear at level 7 and the boots at 14. Since you get the extra stats at levels 4, 8, 12 and 16, you should always level up gear four levels at a time. So if you start with level 4 gloves e.g., you take them to level 8 before you start on the next item. And you don't start to go for level 16 on any item when the rest isn't even level 8 yet. 

Yes, I know that you only need 4 pieces for the lifesteal stat. :) It is my best gear. Ok, I'll try to upgrade all of my gear to 8+ then. Thanks!!!

Use a full team of 4 for now if you're struggling, you can come back for 3* later. And yes, Veteran is better than Scrapper - keep in mind Veteran's damage scales off his defense, so you should try to give him gloves/chest with def percentage as main stat, and def percentage substats on other gear, if possible. 

Ok! Should I upgrade his gear to 8+ too? Yeah, right?

Yes. Basically, all gear on champions that you use regularly should be at least level 8 - that doesn't take that much silver. Leveling to 12 can cost a lot more and 16 can cost millions, so that you can't do on all champions, but 8 yes. 

Here is what i do now ,,,,,

I go to   https://ayumilove.net/raid-shadow-legends-list-of-champions-by-ranking/

I compare my heros to his Listings ,,,  S ,, A ,,, B ,,, C ,,,, F .....

Now with RAIDs new System of identifying heros ,,, 

I mark all the Ones on Ayumiloves page that are S and A with a Heart .........

All the Bs get marked with a >   I

all the Cs get marked with a >   II

and all the Fs get marked with a >  III 

I Ignore the ELITES becauase you never know where they might fit in and they can always make up faction war teams anyway ...

Now I will start to FOOD my Heros from the Bottom ,, I will lvl up the > III without armor

(( sometimes i will drop uncommon on them but mostly I sell that ))

If in DOUBT compare Ayumiloves List to  the list here https://hellhades.com/raid-shadow-legends/ 

They are ususally the same ,,, 

I also Use Hellhades Armor list to Sell off my Junk Armors 

I am also at the point where I am selling off ALL ARMOR that is RARE ,,UNLESS it is 5 star or 6 Star 

OR 5 star Crit rate Gloves ,,, SPEED boots ,,, or  ATT% Chest , with the off DEF% Gloves and Boots

From the Forage i am Selling off Everything that is NOT 5 Star Epic or Better ,,

Unless they are 5 star or Better Speed Boots or Crit Rate Gloves or ATT% Chest

I do not have ANY Uncommon Gear saved unless it is 5 star or better

and I probably dont really have much RAREs anymore unless they are 5 Star or better

I also DONT take any RARE past +8 unless it is 5 Star or Speed Boots

This Game is a LONG HAUL GAME unless you are a CASHER and are Buying the Good Gear that goes on sale 

Both Websites list have a  NEW PLAYER STARTER GUIDE ,,,,

Having seen your roster now, I would agree with the above that you should keep Jizoh.  I'd also put him in my main team and level him to 40.  

I would also keep the other rares for now and focus on use the 1 and 2 star champions for food.  Even if this changes in the future you will want to keep Frozen Banshee as she is a top tier champion for Clan Boss when you get to that (but don't worry about it for now).  Also do not worry about faction wars or arena yet, and focus on using your energy for campaign runs and leveling champs.

Who should I replace Jizoh with??

I think it would be really helpfull for you to watch some beginners guides. There are plenty to find on youtube. Also check out some big streamers like hell hades or ash or chosen. THey have usefull guides and explanations on how things work in the game.

Keep Jizoh, He may not be top drawer, but he has use in some circumstances. I can get him to more or less solo scarab boss on low doom tower for example