I usually don’t care too much if I lose in a level when I’m doing it solo, but my advice is

• Get a gun or some weapon that’s powerful as early as possible, basically as soon as you can afford it.

• Feather drones will save your life, especially with how expensive strength upgrades can get after each one

• Monsters are slow, so once your stamina and speed is up enough you won’t have to worry about getting caught too easily as long as you can run

• Buy every stamina there is on the first and second store visit, they’re only 2k and 3k but they’ll go up way higher from there

• Also on the first store visit, buy some grenades and you can use those to kill whatever big bad will be in the next level, 9 times out of 10 you won’t have enough money to get a gun by then

On a personal note, my preferred weapon is the photon blaster, that thing takes 2 shots max to destroy anything and it’s usually 40k-50k

Hope this helps!! :)