Emerald Nikola Vucevic & Brook Lopez
This is easily the best budget starter/backup center pairing in the game right now if defense and rebounding aren't your primary concerns at the center position. They are basically the same card on offense, just with Brook having a slightly better post game. You can cheaply add gold post spin/dropstep badges to each card if you want to enhance their post moves even more. And gold pick & popper is another cheap badge upgrade that will help to generate more green releases during pick and fades.
Gold Luc Mbah a Moute
For just 500 MT, you'll get a player who can lock up the other team's LeBron/Durant/Carmelo/Abdur-Rahim with a 90 rating in every defensive category. And he's a respectable three-point threat on offense, with an 86-rated three ball, plus hot spots in both corners. His base ratings will also get boosted pretty regularly, since he comes with the powerful microwave badge. For the price, this is a must-have card on every team, even if he only comes into the game with your second unit, or in situations where you need defensive stops.
Silver T.J. Leaf
Another value player you can pickup for 500 MT who has good height (6'10"), athleticism (75 speed & vertical), and offensive ability (85 three, 84 post fade, 83 post control, 85 post hook) for a power forward. As with emerald Vucevic/Lopez, you can cheaply add post spin/dropstep/pick & popper badges to this card to increase his offensive proficiency.
There's no doubt that this is the best silver point guard card in the game right now. Defense is his only weakness, as he can do it all on offense. It would be interesting to see what he could do with gold posterizer added, but that badge is worth so much MT it's hard to justify putting three of them on a silver card.