Brotato

The only thing that matters for this character is your turret, which is going to make this a really simple run but one that starts off quite difficult.

An important thing to start off with is you actively want to avoid picking up any materials. If you pick up a few here or there when trying to dodge attacks that's fine, but mostly just stand under your turret while it does all the work. Any materials you don't get upgrades the rarity of your turret (which is very important because it makes it shoot more projectiles) but also increases its attack speed and range. Your earliest struggle will be that your turret doesn't cover the whole map with its range and that it may fire too slow to kill all enemies on its own. Eventually this stops being a problem as long as you let unused materials do their job.

Start off with a slingshot since your builder's turret takes its stats and effects from your best weapon. This is going to let projectiles bounce to other enemies which is going to clear enemies out all around you. Anytime another slingshot pops up in the store you want to buy another. The goal is to get the rarity of it up as each increased rarity level of the slingshot adds another bounce. I finished the run with a purple, but if you can get it to legendary this will become a cakewalk.

No other weapon really matters. Your damage is going to be low, and the turret is going to be doing most of the work. I bought a bunch of primitive weapons to get the extra max HP for the weapon bonus, but after a round when I checked how much damage they did it was minimal. All damage modifications are reduced by 75% so you are safe to ignore any % Damage, Melee Damage, Ranged Damage, or Elemental Damage improvements - they're unnecessary. Instead the main thing we care about is Engineering as that is what our turret scales on (and we get 50% more benefit). If engineering isn't there, go Harvesting since that's where our experience and usable materials will come from. If neither of those are an option, we want survivability - dodge, HP regeneration, max HP, or armor.

Early game feel free to leave your turret's side if you see a tree spawn to break it and see if it has a loot crate since more items is always nice, but once your turret is set up you can largely just stand still under your turret every round. The first few rounds - when projectile shooting enemies and the larger enemies that charge start spawning you'll need to make some mild movements to avoid their attacks so don't get too comfortable standing still the entire round until your turret is destroying everything.

You won't make a lot of money in this run so you want to be picky with your items. Make use of locking them, never pass up on engineering improvements - especially if they are the unique ones that increase fire rate, give it the chance to crit, etc. Get your slingshot strong, get your engineering up, and remember that you can take as many damage reduction items as you want as long as it boosts another stat that's more relevant. Follow these steps and by the time your turret goes legendary this run should be a guaranteed success.

Good luck, have fun!

Turrets can be purchased from the shop in game for materials they will appear in the shop as a turret to buy or can come with an item that can proc a turret spawn (Upon tree kill spawn a turret), simply have 5 of these on your map at once and the achievement will be yours. This achievement unlocks the Engineer class

Edit: Pocket factory (Turrets spawn from killing trees) DOES NOT count towards the cheevo therefore you need to purchase 5 different turrets from the store

Despite the description, the achievement isn't ONLY for actual turrets - it also applies to (at least some) other permanent structures as well. I got the achievement with no "turrets", but five gardens, all of which were created by the Pruner weapon, which creates a food-spawning garden on the map.

I was using the Pacifist class (unlocked by collecting 10000 materials, which will come naturally over a few runs), and I'd recommend that for this achievement - the Pruner is a starter weapon option for that class, and once you've got a weapon, additional copies of that weapon appear more frequently in the shop. After you equip a fifth Pruner, the achievement should pop at the beginning of the next round. I didn't specifically note which round I got the achievement on, but I believe I had it by round 10 or 11.

Because I got the achievement with five gardens, I can't confirm with certainty whether multiple structure types work (for example, three gardens, a Tyler, and a Medical Turret), although my assumption is that they would.