1. Find something that YOU like
2. Find something that's good right out of the box (fit/finish/detail/accuracy).
Like WWII ? Try Tamiya: Stug IIIG, Mobelwagen, Panzer IIIL and IVH, Marder III or IIIM, Wespe, early/mid-production Tiger.
Try AFV Club: Hellcat
Like Modern? Try Tamiya: Japanese Type 90 (probably THE best kit out of the box), Leopard 2A5, Russian T-55.
Try Trumpeter: Swedish Type S-C. (The "B" isn't quite as detail-oriented IMO) or the British AS-90.
Try AFV Club: M41 Walker Bulldog
Just a few suggestions; let us know how it goes.
Gip Winecoff