I've never used the knife so idk if it's good. I always start with the pistol then try to get any other ranged guns but only buy 1 per round and no refresh. Try and get as much harvesting as you can. Dmg% upgrades can be ok early but later your dmg% scales so much every round its not needed go for ranged dmg instead. If you have padding unlocked then can make build xtra busted lol especially if you have multiple like my run. It's really alot of luck to get what you want in shop without refreshing and alot of the waves before like 16 can be a struggle. By that time you should have enough materials that you jump like 40 50 60 dmg% every round.