i believe it takes 100+ posts for you be senior, i have seem some dude on 113 posts and he is senior, it could also be a time thing, who knows but i would say more than 100 posts.
on the topic, go for a motovert, pitster pro x3 / x3r, agb29 with the extra money left over for mods, and i believe fmr are coming out with a stock 138cc bike in the near future you may want to look into man. check it out.