Were all your champs surviving till Dragon? If so, I'd try Farahkin the Fat instead of Torturehelm since he's already 60 too. Either way, that's huge you're doing it now. The gear you'll get will make the stage easier.

Also, don't try to progress further in Dragon yet. Stage 20 is the best Drops-to-Energy ratio outside of Hard mode, it's what most of us still run during Dragon Dungeon events

Skip Ultimate Galek.  Focus on a better build for Ninja. Ninja is a far superior toon.    

How long did it take you to achieve LVL 20 Dragon Defeat?  As .5 month player ( half of a month ) , it seems too tedious to get anyone above 3 to 40 , nonetheless to 60, F2P .. 

But LOL paid options don't grant champs... The heck RAID SHADOW LEGENDS?   LOL 

I believe that there's a promo code still for Ninja for New Players but you have to redeem in on Day 1 or so? If you're only a few weeks into the game, it might be a good idea to start a new account and use that promo code. Ninja will be a huge boost to your account right at the start and will get you right back to where you are now in a matter of days

EDIT: Just checked Pocketgamer and yes, that's still a promo code.

NINJARETURNS - Ninja, four energy refills, and 4x 20 multibattles 

If that has expired, this one might still be working:

MonkeyKing: Sun Wukong, 15x Spirit XP Brews, 300,000 Silver, 15x Greater Spirit Potions 

Here's the sites

https://www.pocketgamer.com/raid-shadow-legends/redeem-codes/

https://ayumilove.net/raid-shadow-legends-promo-codes/

There's a bunch of existing Promo Codes you can also use every day afterward. 1 Promo Code per 24 hours, just make sure the Ninja one is the first one you use. These might not be current, I know the amberfall2gt is the latest one

 Hello, sorry I took so long to reply.

I am f2p, short answer is. Took me i think 5 or 6 months. I like the game so I don't pay attention to how long it takes to me do this or that. But it was about the time I got Lordly legionary as a monthly rewards.

the long tip:

 I kind of followed the tips of the hellhades page. Focusing first on leveling up a character to lv 60 to be able to farm food champs and opens lots of shards during events to get champs that's are graded at least 4 stars in general.  Then level those up to 60. 

Pick a team and marry to it for as long as you can. If it's at least 3.5 star rated then it should be usefull for at least the normal dungeons. Put the best artifacts you can get on them. Money is easy to farm once you get to D20 (i'm selling every 5star gear I get now and they sell gooooood)

 Also pay attention to roles. Pick a damage dealer, two supports (one healer/reviver and someone who increases the damage output of your party) and  a debuffer (warmaiden is the best). 

Sinergy  is what matters the most. Imagine if you do as the tutorial shows and go with only nukers. Dragon is gonna destroy it. But having a decent healer, a debuffer, a team that can defend the nuker.  you're going to do waaay better.

The tip I got here about using stun set is really usefull too. CC helps a lot to get throw waves with your party intact. 

 I never could claim the wukong code because I played for like two weeks before I learn about codes and I want to kill myself everyday now 😭