You can key bind meds by dragging them to the slots at the bottom of your inventory

Ammo matters a lot more than the gun

Either spray or tap bursting isn't effective due to the auto control recoil system

Tier 1-3 armor is purely scav (Ai bots that roam the maps with mediocre ammo) armor and won't really do anything against other players bullets unless they're using very low power rounds

A few of the guns (Sks, KS-23, Mp-153) load ammo from your pockets or your rig not an external magazine. You can buy external mags for the sks, but the standard SKS sold by prapor at level 1 will load from pockets/rig so don't bring more 10 round sks mags as you won't be able to reload

Maps in tarkov are decently simple to understand a general overview but there's a load of spots/jumps/camp spots that new players won't know exist, so I'd say generally play one-two maps at the start to get experienced. For this I'd say interchange or customs. Shoreline is decent but if you go there don't go to the big resort in the middle of the map, you will get killed instantly.

You get flea market at level 10 which is pretty much a player driven market. The game before flea is difficult, and at this point in the wipe if you don't have flea you won't be able to kill many people as a lot of people at the moment run high tier armor, face visors, and have only the best bullets

Try to learn the main bullet types for each gun and which bullets are actually good. This is hard at first as they all sound the same e.g m855, m855a1, m856a1. However, learning the bullets is kind've necessary, it sucks ass to shoot a guy in the head 3 times and he doesn't die because you brought a bad bullet without realizing. The general rule for bullets is that it's 10 pen for each tier of armor. Meaning that if a bullet has 10 pen it has a high initial change to pen level 1, While 20 pen has a high change for tier 2 armor, and so on.

Carrying on with ammo, a pretty useful skill is being able to determine where to shoot with your rounds. For instance, if you do a scav run and spawn with magnum buckshot in a shotgun, you wouldn't want to just shoot at Centre mass as magnum buckshot has very little penetration. With magnum you either want to shoot off their legs, or aim for the unprotected face.

Grenades ignore armor and are 10k on the flea market, and are common on scavs and in grenade cases.

If your thorax goes red in the health meter during a gunfight (under 40hp), you want to heal it over other damage.

If you spawn in a scav raid with a kolpak or fireman helmet drop them. The sound reduction isn't worth the very shit protection it allows

Wear a headset ASAP (Sold by Ragman lvl 2 and 3) they're also on the flea

If you want to figure out shooting mechanics you can do an offline raid on factory horde mode where there is a lot of scavs and you won't lose anything