If you need to meet the required spendings with traders to level them up, here are a few tips. Note that pretty much every interaction outside quests, counts as spendings: Insurance, repairing, selling, buying as well as bartering.
Therapist, Prapor and Mechanic are no problem when it comes to spendings. Prapor is used for insurance and you will eventually buy a scav junkbox (or three) from Therapist for 1.1M each. I recommend using Grizzlies to heal up after raids and not pay her for it as you would miss out on the experience gained. Mechanic gives the most money for weapon (parts) you bring home, so naturally you will sell to him a lot. Ragman is also OK as he gives you the most for wearables.
You could have an issue with Skier, Peacekeeper and Jaeger.
In general I would recommend the following:
Skier – once Mechanic is satisfied, I sell the weapon parts, ammo and rigs to him. You can also use him to repair your weapons (ideally before selling them to him).
Peacekeeper – the easiest way is to buy ammo from him, but he also buys all intel items (diaries, cookbooks, SSDs…). You can buy those on the FM, the only issue is that this converts your RUB into USD which is not optimal in the beginning, but you will later use those anyway for a quest and you will most likely end up buying ammo from him later.
Jaeger – buy melee items from the Flea market and sell to him. Some things can even net you a bit of money. For example the Antique axe is bought for 56k and you can sometimes find it cheaper there (people sell them there to increase the FM rep.) Other weapons work too without loosing a heap of money, experiment a bit.
Best of luck and see ya in raids!
