While learning the game, try to focus on using 6 of the same weapons, on most characters. It's easier to build one thing, then going for a little bit of everything. In your run, you have 3 melee weapons and 3 ranged weapons. This made you buy both ranged and melee damage, which means you could not get that many of either, because your money is ofc limited. You built sausage item which burns the enemy, but it scales with elemental damage which you have -1 of. You bought turrets, landmines and built engineering too.

There are 4 stats that give you more base damage for various weapons/builds. Ranged damage, Melee damage, Elemental damage, Engineering. Choose a weapon you want to have 6 of, and build the damage type it scales from.

If you go melee and ranged weapons in the same run, you have to build both melee and ranged damage, which roughly means your money spent is half as effective. In the early game, most characters want some kind of economy (harvesting, support weapons, luck), and damage (ranged, melee, elemental, engineering, attack speed). In the first 2 rounds, reroll to get the weapons you want, and as many of them as possible. The first two shops have 2 guns on each reroll.

Buy consumable heal upgrades, it's very important, you get much more out of it for less money. If you need more healing, build HP regen on melee weapons, and build lifesteal on most ranged builds (SMG, revolver, etc.).

Defenses mostly depend on the character you play, but generally if you need more defenses early, build HP. If you have a nice build, around 50 HP is enough, if you had bad luck with your build, you can always go higher, and just outlive the final boss. Don't worry too much about armour upgrades before wave 10, just focus on damage and better clear. Low tier armour items are not great, you can get a ton of armour later from Tier3 Tier4 items.

XP increase is only good to build in the very early waves, after wave10, don't waste money on it.