You do not need fancy strategies. You need to tank bosses and mow down enemies with cheap firepower.

1. Forget the melee. You will have plenty of ammo.
2. Forget the shotgun. Slow and unreliable.
3. Forget explosives. Too situational.
4. Clear rooms from their doorways. No risk of being surrounded or surprised.
5. Always clear floors. More points – more ammo.

On the first floor, strive to only use your pistol. Headshots are easy enough on zombies and dogs.

In the first shop, spend all points on the submachine gun and its ammo. Use the submachine gun in the presence of ghouls and burning heads, otherwise use the pistol.

In the second shop, buy the revolver with no additional rounds, as you'll rarely use it and should naturally pick up more than enough for boss fights. Ensure that you have 3 Health Drinks to tank the first boss. Everything else goes into submachine ammo. You may still use the pistol for strugglers.

In the thrid shop, make sure that you leave with at least 300 submachine ammo. If funds remain, procure Health Drinks and more submachine ammo. From now on, the pistol is to be used only for mimic checks.

For the forth and all subsequent shops – maintain your submachine ammo at 500, which will be more than enough. Everything else goes into Health Drinks.

The submachine gun will cut through everything. Only exceptions – knights and bossess, but dealing with them is extremely easy. Clear their minions first with submachine fire, then shoot them with your revolver until they are dead, including so point blank – do not bother too much with running/evading, as it will mess up your aim; just heal from your vast suppy of meds.

Congratulations, you have escaped.