I like to play against other rl people, the bots get kinda easy once you get the hang of the game. I do wish those bugs were fixed, they make a lot of the more defensive/tanky strategies unviable right now.
Some tips:
This guide by Latios is really extensive and helpful, give it a read:
Get companions with intersect to put on your front row (kits, furmus and the purple brother deer), they increase your longevity.
Save up paws in the earlier rounds so you get some extra as interest each round (10 saved paws gives +1, 20 +2, 30 and up +3). This gives you more paws in the long run.
Getting a bunch of pack mentality companions lined up is very good. There are quite a few companions with that passive so there's usually a few in the pool.
And if they're available, get a zapscour or two, they're probably the most powerful companion in the arena because of their power/speed and ability to attack twice each turn.
Five tactician is very nice, the +20% damage and 50% crit chance are amazing to have. You'll probably want a powerful attacker to make use of the boosts, the double tactician creatures aren't that strong by themselves. I like to go with grimalkin, bracchus or echecara. Kuzma are also fun to combine with this, they do massive damage on a crit that will one-shot pretty much anything.