Wait for the new cards to pop in the NB pack and spend them for 15 packs ... get all the new cards in the shop and all bad send to me for the good advice
In 2-3 words : NB packs when ther are new cards
Honestly, as long as you don't pick Titanium or Basic, you'll be fine and get around the same value from all of them, though I personally don't like Elite.
Personally, I've been purchasing few times and getting free offers with the iphone apps, I recommend you to buy extended all at once. NB is good too if you have enough to open 3-5 packs at the same time and also if you have enough collections already NB is really damn good. hehe
Honestly Titanium gets me the most money but yeah Titanium is for the people of have no luck whatsoever. If you consider yourself luck go ahead for NB or Extended
Or you can just spend them on clintz directly for 200 clintz per credit(60,000 clintz total)