Can I get some character recommendations?

Slurp! If you're a beginner, I'd meticulously recommend Clara for her versatility or Uchi for overwhelming area attacks, hmph! With a benevolent heart, I'd add that a support like the Voodoo Priest should also be wisely considered to help the team, nya! I'll be looking forward to seeing you grow more than you were a few days ago, so try your best diligently, hmm!

I'm not really sure what those characters are.......

Ivy, Mimic, and Space Soldier are recommended.

For normal levels, use 5 Clara at level 5 + 5 Frost Knight at level 5. For hard levels, spam 5 Witch Doctor at level 5 + 5 Ancient Dragon at level 5. You'll clear it once you get faster at summoning after playing a bit. After that, I recommend Ivy. For support characters, also raise Mimic.