Thanks for giving it a go!
There’s definitely some upgrades that are better than others. I know early game I like to prioritize Decay Rate and Resources, and start getting more Damage and Attack Speed. I usually save the upgrades to Experience and Spawn Rate towards the end.
Actually after playing it some more after submission, I think the Experience upgrade is a trap. Yes you get more upgrades quicker, but it means you kill less enemies and get less resources, which can cripple a run for sure.