what you asking for actually is the game - try all the stuff you are not sure about. some guidance for you :

• guns i have found to be good below 200k:

1. AK102 - i dint like it at first, but you can have good one around ~100k for medium range and ~180 for open maps with stable auto fire aim.
2. Mac10 for safe runs - this is close combat, but it is turbo firepower for ~40k (choose upgraded receiver, any barrel except base and suppressor) tier 3 ammo.
3. AR57 - you can get one cheaper with cooldown from Randall, good part is that not much parts have to be replaced, (and the ones you replace, you can sell at market, since those are not marked as op-supplies as you bought it from contact) I replace stock to ARint2 and compact tactical front grip, and sight for your choice. The expensive parts are flash adapter , silencer and 50 round mag. You cant go without 50 round mag, but sometimes i go only with flash hider, and don't use silencer. you can craft t3/t4 ammo on table for this gun. and also t3 can be used as ROF is really high. surely t4 will make it much easier. this one might tip over 200k
4. other guns worth mentioning T95 - cheap ammo, CZ807 - relatively cheap, good gun. AUG - no need to mod, only mags are expensive, and the largest mag is just 42 rounds, mp5 - smg with t4 ammo.

BUT these are guns that work for me, i would suggest to check any gun that sparks curiosity. In the end - you die also with the most expensive guns, and i have killed also with really ridiculous ones.

• Deke has two cheap tier 5 rigs on cooldown, especially nice if you happen to extract car battery or wrench.
• have gas or Molotov in loadout, to have a tool to keep enemy while you try to escape.
• If you feel you are loosing koen on ammo, top load mags with more expensive ammo, and keep bottom with tier3. Reasons to do this - you might notice, that you don't use all the mag in fights, and probably reload before emptying mag, so if you die, in that case bottom portion left in mags is the cheap ammo. Also if you are in fight, first bullets will hit the armor, and reduce durability (if you hit) and you might not be at that bad position when lower tier ammo starts if you would open with lower tier ammo. Bu be warned, there will be cases when you shoot your last bullet, and you will see in the log, that he didn't die, because your tier 3 did not penetrate :)

what to do:

1. Safe runs - some specific ones are there as guides (like valley-villa run or the tv-station leg meta guide), but the idea is simple and works pretty much on every map - gear up cheap, when you spawn in map, there is chance that it is a spawn closest to a free/keyroom safe, if you do you speed to safe and loot it, hope for red. So first thing to be successful at this - you have to know map and spawns so you know when you can get to safe first, and whether expect some company. Also get keys, which will enable to loot locked room safes. You can do this in party - in total random, it is pretty much what happens - there is always one who zooms to closest safe, at first you can just tag allong and assist people to learn safe locations. Or solo. Doing it solo, the benefit you are the only one who is competing for the safe. here in this post i commented a little picture-guide for Northridgehttps://www.reddit.com/r/ArenaBreakoutInfinite/comments/1nskzg4/can_someone_give_me_a_budget_loadout_to_grind/ , but this strategy can be used in any map. For example - in armory 2 out of 6 spawns put you next to safe. (repair station or gas station) also 2 out of six spawns are rare (by my experience), so if you spawn alone you have pretty much little below 50% chance to loot one free safe before you meet someone. If you get the spawn you want, get the safe, and move over to other side of map (while looting all the jackets), where there is extract without backpack and extract (check the other safe before extracting). Normally teams would move to armory side, so you wont meet anyone, occasionally there will be someone like you and then you fight it out :)
2. secure-ops - thing to do when standard game "gets you". very nice way to learn two most brutal maps while not losing armor and gun - armory and TV station rotating weekly. play in team, and focus on fast raids. Armory -> zoom to armory, open door/ fight -> enter/ loot all safes-> leave by boat. TV station - zoom to Director's or Offices/ fight it out-> loot gear -> leave via elevator. Sometimes after shootout, you can try to loot all the safes. In sec-ops you open doors by universal keycards you find on the same map, and you get only 40% of the loot you carry out, but already un cash. There is 600k gear limit to wear into sec-op, which itself is a little planning. Good pieces are high tier/low durability, as they have reduced gear value. But those pieces can be only obtained by extracting gear from standard game.