Any general tips and tricks for beginners?

For starters, I played Dota and Mobile Legends, so I kinda get how MOBA games are played out. Since this is a new game, I want to know the pacing of the game (when to ult, when to push, when to farm, when to gank, etc.), and a good Pokémon for starters.

For my Pokémons, I have been spamming Blastoise and Lucario. (Please correct my build) My go-to Blastoise skill-build is hydro pump and surf. Very fun coz people are constantly cc'ed. My Lucario would be extreme speed and bone rush. He's also very fun when he is just blinking from 1 Pokémon to another.

Lastly, what held items should I be prioritizing in levelling?

I'm currently Trainer Level 13, and I've played rank 3 times.

Edit: Thank you so much for the tips and guides! I can't reply to each of you but I did read them all.