With LLC being so expensive, I'd stay DBA for now, as there's not a lot of liability in being a reseller (depending on what you sell, of course).
I'd plug for it once your annual net income exceeds, say, $3,000.
In my state, LLC is cheap ($100ish), so I bought mine and have already repaid the cost several times over. I did it as a preliminary step to have settled once I start growing in earnest. I haven't had time/energy yet but my one customer keeps me going so far.