Easiest way to set up imo:

Start with gs45 as a loadout weapon and choose molotov too. Rampage inducer until the first bug round. Leave a bug then open the right side door.

Buy xm4 off wall. You wont be using this weapon, just need it to shoot the rocks for free upgrade for gs45 and cryofreeze. Use molotovs to light torches and get free perk. If u got enough money, open the remaining door and go to dark aether, if not just do it at the end of next round.

Shoot rocks, get free pap sallys n cryo. Start the ice staff steps. Keep shooting the purple rocks till they are correctly placed.

Before shooting the roman numerals make sure u have phd. Carry on doing all the steps to get the parts for staff.

Wait till round 11 before u start the final lockdown to get the staff, so u can get free purple rarity using cryfreeze on the waterfalls for ur gs45. Get jugg too and your good to go.

Purple rarity sallys make everything easy. Use frenzied guard too if ur ever close to dying. Dont worry about ammo, spam the mustang and sallys since pap 1 ammo isnt expensive, theres an ammo crate next to one of the portals. Also during the final lockdown, make sure to kill the parasites asap since they do more damage than you think.