Well if you are looking for Gambit I don't think you'll find much in Bronze Age because I don't think he came into play until after that era. If you are looking for sketch cards, Bronze age will give 1 per box, the odds for Beginnings 1 & 2 were 1:3 boxes.
Personally, I'm going to buy a box of Bronze Age and a mini master set of MB3 from a rip-n-flip dealer. I bought 3 boxes of MB1 and didn't complete a base set, die-cut set, or prime set. Pulled 1 sketch, 1 holo, 1 printing plate and a bunch of auto comic covers. As a collector I thought it was a huge loss.
If you can afford to buy cases, you are in a different boat from me. Not sure which is better - but I don't think the Rittenhouse stuff holds much value unless you pull a 'premium' sketch. You normally get a full base set per box, so they tend to sell pretty cheap. You need to buy an entire case to make the subsets. I think that if you buy a case and don't make all of the subsets, you can file a case with Rittenhouse they will send you whatever you missed (except you usually have to cash in your wrappers to get one subset card). The Upper Deck stuff probably has better resale value for anything you don't want to keep, but the randomization isn't nearly as good. I don't know what a case 'guarantees' you.