technically, the long tail cast on also completes your first row by making a row of purl bumps, so a lot of references will tell you to then start your stockinette with a wrong side row.
that said, i generally use the long tail cast on and always start on the first right side row anyway, just as i would for any other cast on (as i’m sure many others do, also).
There is a difference of opinion on the long tail cast on. Some people say that the long-tail cast on should count as a row when working stockinette stitch. Others treat the cast-on as just a cast-on and count the first row of the pattern as the first row.
I happen to be one who doesn’t count the cast on as a row.
As for the right side, or wrong side, your pattern should tell you if the first row is a rs or ws row.
If you’re working st st, you can purl the first knitted row and call it row 2, or just knit the first row. It really isn’t that big a deal for straight stockinette.
Personally if a pattern says to cast on and then knit X number of rows, I do just that.
I just recently heard about the `advice’ that you should work the first row after the CO as the WS row if you do a long tail cast on. I’ve been knitting since I was in high school (a very long time ago) and usually use the long tail and just do the next row as written in the pattern. A cast on is a cast on and a row is a row.