TheGT.net is one of the oldest Greek trackers out there and now-days is also one of the few still online. They have a big user database with approximately 58000 users (as of today) with about 17000 active torrents. The torrent that are being uploaded on the tracker are both from scene releases and also from its encoding teams (which allow me to say do some pretty good job). It has encoding teams for tv series, movie rips, HD-movie rips and music.
Being a new member on the tracker doesn't mean that you have to strive for keeping ratio, since almost all the HD content they offer is freeleech and also anything "famous/good" might be on a freeleech as well. Also there is some high activity on almost every new torrent added. They also offer many internal movie releases with either embedded (Greek) subtitles, or else given in a separate .srt file. Unfortunately bad news for new users is that the tracker currently uses the waiting time system, thus any new users will have to wait 48h before snatching any new torrent.
As for the invites. 1 invite is given on every member being promoted to Power User (unfortunately when being promoted to Super User you get none) and can also be bought (in packs of 2 per purchase) through the bonus system, though the price is kinda expensive (about 2000 seeding hours for just 2 invites). As an extra, VIPs are given invites when they donate. The tracker currently is considered to be invite only, with the invitation being open for specific amounts of time and for specific user classes each time (can be Power users and up, or VIPs and up).
As for the screenshots, here they are:
Karma Bonus system