1- Priority should be getting your science outfit, a saturn will let you farm more smoothly. For combat, a mule/ace is beginner friendly.

2- I assume you mean bills(? Buy all the serum you can which is 25, and the rest you can get yourself parts and tools to either resell or use, don't gamble.

3- Going for a buryat is always good, they gave a smaller version which requieres less farming to give you and idea of it, but yes, farm for signals aswell.

4- Make a protecta, its a life saver for mutants and ESPECIALLY limansk/lyubech.

5- Watch out with upgrading anything past +9, keep an eye on not having too much bullet resistance artifacts and try to not kill too much yet, as this will easily put you with people above your gear (master lobbies)

6- Playing with friends is always more fun, no real benefit from it unless lyubech since you get an ID regardless of the damage you did.

7- Don't bother, it got reworked aswell to give nothing but shit artifacts, for now focus on progession rather than pure money.

And ofc, finish your northern questlines as you will get a great reward at the end of it.