Is your true concern to get on those sites or just have your music avaliable for purchase. Depending how how you want to direct visitors, whether your promote, have your own website, etc. Bandcamp is an excellent service to distribute on.
Well, you either get yourself on a label or you distribute yourself via Tunecore or CDBaby. That said it's probably not worth trying to sell your music on your own if you don't already have a fanbase. You're not going to get paid and fewer people will hear it.
I would suggest CD baby for iTunes etc. They've been around longer and are cheaper than TuneCore, and I've taken exception to some of the misinformation one of the top Tune Core guys has been spreading.
ISRC's are free despite what he says, and although yes, they don't have much to do with royalties, they are in fact a standardized reference that can be traced to the owner of the recording. They also aren't governed by RIAA looking to drain the lifeblood from indie artists, this made me realize that they're really the only ones charging lots of money to artists, since it's about $60 to do a record and they take it down if you stop paying yearly renewals. (about$30) Very odd because it literally costs them $0 and takes 0 effort to leave it on the store, (y'know because it cost $30 in electricity to host 45MB on their server) but if you have 5 records as any normal established artist might, paying $150/yr. you can see where they profit greatly. Not to mention there's no guarantee they don't raise renewal fees as they have in the past. Figure 5 records averaging 5 years each, you're giving them $300 in sign up, plus $600 in renewals. It may not be completely breaking the bank, but CD Baby seems the better deal. As far as I've seen CD Baby is one (cheaper) payment and up forever.