Well there's the one month free trial period so try that and slso watch some vids to see the gameplay if you haven't already.
Also the activeness at certain times depends on the server's region usually
(I.e NA, EU, JP )
Also most ppl will be at endgame but there will still be a handful of ppl who are new too and will be running around the low areas.
Playing with other ppl (i.e potential future friends ) can be a bit tricky at some points. So just try and find an fc that takes in all players and isn't a mass fc.