It's not just on you, goal would be for it to be clear for everyone (I had some people that weren't sure too)... You don't find upgrades, you buy them! There's 2 shops upstairs in the lobby you can use your coins in. Maybe should've made that clearer somewhere!
Also weird that you didn't get any special room, maybe you were just unlucky with the map rng. It should give you alot of special rooms in the first few rounds you play - maybe I should've used a set number of rooms instead of a random number of rooms...
Thank you for playing the game despite this!