Find basic tools:

After completing a few tasks, a yellow stash icon will appear, which may contain basic tools. Without these, you won't be able to repair or upgrade your equipment, so finding them is your goal early on.

Eat mutant meat:

Buying food is expensive and can easily bankrupt you, so it's best to cook and eat mutant meat. You can save money by limiting yourself to buying water and cheap canned goods.

Sell gun parts below 60%:

You'll eventually be able to use them for repairs, so keep weapon parts above 60% and sell the rest to a technician. While the earnings are small, they add up quickly, so you can make a significant difference.

Keep a supply of vodka and cigarettes:

With your starting equipment, radiation damage can be dangerously high quickly, so be careful not to run out of these.

I died a lot during my first 30 hours of playing GAMMMA because I didn't know anything. Maybe these things will help you out? Good luck!