Your best bet for catching up on the whole series is to buy the first two trade paperbacks. They aren’t as good as the comics, or as large, but unless you’re either rich, or really determined, you probably won’t be able to collect all the back issues too quickly. The last issue of Street Fighter was #14, the first was #0, but that was a con exclusive, very hard to find, and wasn’t as long as a normal comic, more of a teaser really. All of the issues are in the trades, in order. If you have a credit card, you can order them online from www.ruppsworld.com or www.herofix.com
If not, you might want to try eBay in your own country, or a comic shop if you’re lucky enough to live close enough to one for a visit. The trades are great, but the individual comics are even better!
Darkstalkers is up to #6, and there is a trade paperback of those issues as well.