still can't get robux - what am i missing?

if the problem is not having a card on the account, roblox gift cards from a normal shop are the easy way round it. redeem the code on the website and pick robux or credit. that's still buying, just without a bank card.

You buy them or you earn them, there's no third route. Premium pays a monthly stipend, and anything you sell yourself comes back as robux - though selling needs premium too. Free robux for a survey is someone taking your account.