Grace, abnormal, and aaabat has given you good advice. http://urdb.kirlad.net/packs.php would support their suggestions.
if you're looking for the best "usable" cards per credits then you'd probably better off staying with new bloods (especially since they've added that DT incentive to play standard)
Nevertheless, i personally swear by titanium packs
. I find that it's the best way to build up collection. You do have to live with the possibility of ending up with useless cards, but hey' it's a card collecting game and it's worth it (at least for me personally) to choose the clans where you still have 0/xx cards or less than 50% of any clan. Saving up for 300 credits from doing DTs and ELO
also makes it more "rewarding". However, if what you want is best moneh or Hax
cards per credits, then go with newbloods or elites.