you can't trust new bases before testing and even then you may only have a few cards from a specific bin in that base anyway, and never buy non-refundable cards and you have to test them within their given time, on top of that many other factors may trigger a false positive such as the card being out of funds but enough to approve their test transaction or simply a bug in their checker which they will never look into or care about, it's not like you have customer service with these things.
You also don't have any reasonable infrastructure for carding and you're not sure about what you're doing yourself so i think you should reconsider your ventures or look for experienced help. Also keep in mind in this game you can make a lot but not before you lose a lot specially dead cards/bases i sure learned that the hard way after buying over 1k worth of cards only to have all of them die after a couple of days (bank probably got a hold of the info about the leaked cards and they likely froze all of them) even a base that's been working for a while can die overnight, bins can also get blacklisted on shops and whatnot.
Cards I've been buying lately I get about 75-80% refunded/doa, banks have people checking these shops already, companies are informing banks all the time without public knowledge (you also don't know where they came from anyway so it's not like you can check the news) most cards are doa that's the reality we live in.
Hopefully if people keep refunding these cards the shops selling them will eventually realise how much money they're losing on dead cards and will be more picky.