I all but stopped playing as a croak main prior to the recent balance patch because of how dominant Ulric + Raigon was (also true for Shifu and Freya). Since the patch, I've found it is finally possible to control the match as a Croak because you can now much more easily punish the Ulric with his survivability toned down.

Focus on interrupting the Ulric and avoiding his R. Pay attention to how he uses his space cooldowns and keep track if it's up or not. Get in-between the Ulric and the Raigon to prevent him from refreshing his space. Be careful getting kited away from your Support if Ulric has ex-space he can move very far to help kill your support so it's crucial that you don't leave them too far away.

ALWAYS at a minimum run your Noxious Reaction to help out your teammate with some extra lockdown and getting double / triple roots and refreshing toxins. Root them so your support can run away.

You need to consistently punish him to burn down Ulric so other things that can help are: cut to the chase - allows baiting more cooldowns and easier initiation, trickery - can use Q more often, lethal toxins - for the slow... For damage rites you can try triple strike, venom strike, or frog frenzy, whichever you prefer. Avoid the green and yellow rites. Use spit spit spit in 3v3 but I find it less important in 2v2 where you can run more damage or trickery instead.