Vehicles combine empty APCs, IFVs, Tank hunters and Mortar carriers.
1.AML 60 -> AML 90 LYNX
AML60 is a very cheap Mortar carrier (20$). A great start if you want to get a feel for Artillery. I advice getting them in a set of 8, but some people or content with 4 and I know someone who plays with no less than 16 at a time.
They are close range for arty and carry a lot of ammo. Keep them behind your tanks let them shoot at a target and as soon as they are done move them around, because a good opponent will counter fire with his artillery. They dont need as much ammo as normal artillery, but do their job equally well when used on mass.
AML 90 LYNX is the cheapest tank hunter (15$), but it wont actually kill any tanks. It basically a tin box with a potatoe gun screwed on.
So why buy this piece of junk for 15$ you ask? Well the enemy shoots at whatever he sees first, so sending 4 LYNX in front of your tanks will give your tanks one or two shots before recieving counterfire. The LYNX wont hit, but they will tip moral in your favour.
Also if you are not sure if a location is save and you dont have any empty VABs to sacrifice, just send a LYNX.
2.M113 106mm RR->M150->M901ITW
The M901 ITW (55$) is a lightly armored tank hunter that carries enough ammo for one match and wont explode from the first mortar hit. Hide it behind your tanks and micro manage it to target the enemies MBTs and other heavily armored units. I advice buying 4 for maximum killing power.
Be sure to keep it away from enemy artillery fire and use its great maximum range.
The M113 106mm RR is also a great unit to stun the enemy (7AP). It wont hit anything, but for 10$ a piece the enemy morale will drop quickly
3.M151A2 TOW-> I-TOW
Has the same stats as the M901 ITW, but for half the price. There are 2 drawbacks however:
1.Only 4 ATGM per vehicle, so after 4 shots you have to ressuply.
2.No armor at all. A Mortar round looks at this vehicle from 20 yards away and its dead.
4.M2 Bradley IFV->M2A1 Bradley IFV
Just as expensive as the M901 ITW (55$), just as good with the ATGM and just as well protected the M2A1 sacrifices some ammo storage for an Autocannon. If you expect a big amount of lighter vehicles it is really worth having in your deck, just make sure to have enough resupply near by. Some people like to use the Marder1A3 instead which is not as good with its weapons, but has good front armor (3 instead of 1)
A 20$ Tankhunter that doesnt really kill tanks. It basically fullfills the same role as the LYNX, but with better front armor and a better gun. Hide your tanks and place 4 VTS1 out in the open is often an easy way to draw the enemy to where you want him. Some people like to use the Marder 1 instead, because of its autocannons Stun effect.
Another recommendation by "Ribar". It is slow, vulnerable and has an extremely short weapon range, but it will stun anything that gets to close with its flamthrower and kills infantry like a charm. Embed it in your defensive line and it might just tip the scale when you are attacked.