I just joined and have been really enjoying the game until I got to the Cereth boss fight. Don't get me wrong, I love being challenged but I feel like I'm doing it all wrong!

I bought a lvl 58 to find out I couldn't use him in the battle, bought another lvl 15 and increased the party size and I manage to defeat his two minions, but I always end up with him at 70 health knocking my last sylesti unconscious.

I'm so frustrated.. I also keep having to pay for the revitalization of my party which is really draining all my money.

Can anyone help me/give me tips?

Hey there! Welcome! It can be tough to beat the first few bosses that show up. I see your post has been up for a while. Have you managed to gank him yet? In either case, the user Flute has made some really helpful guides, so I'll point out the ones that helped me the most!

This guide covers just about everything, and is very useful for new users! I linked you directly to the post about Tanks & Cannons, which helped me build my first team.

This one is all about how to spend your level-ups and proficiency points to maximize your party's effectiveness! It also covers gear, and which equips work best with which pets.

Also, if you disband your pets from your party, they will heal on their own little by little (as long as they are not unconscious). I didn't learn this until later in the game...but once I knew, I made a second party so I could switch out my low-health pets with fully revitalized ones.

I hope this was somewhat helpful to you! If you have any more questions, I can try to answer them for you, though I'm certainly not an expert.