@General T. Winters (3 July, 2015, 3:55 PM UTC):
It really depends on the players' needs...

If they want to build defence/offence troops, Uranium/Titanium Deposits are going to serve them best.

Credit Deposits if they're trying to maintain a large force (*Ahem* BiohazarD   :P)

Bioplasma Deposits to create more Bioplasma troops, and Crystals for Black Market purchases in general.

Well if you hold a crystal deposit and use the crystals to heal bcs, on the largest crystal depo (20 per hour) you can do 13280 offense worth of bcs per day.  with the largest resource  depo you get 72k per day, which if traded for the res you need to build bcs gets you 6975 offense of bcs per day.  The largest bioplasma depo gives 1500 per day, which if used to build sandworms (the most cos efficient bioplasma unit) gives you 22647 offense per day.  Of course if you save the crystals until you have a 50% discount (or higher if you can get one) you can get 26k+ offense per day from the crystal depo.  

I think, best combination is a crystal depot and a bioplasma depot.

Just build elite sandworms in a non stop "free" que from the both resources got on the deposits

Yes that is good combination but while your at it buy some other elite bioplasma stuff too