What gear should i use after getting full pvp Maiko?

I'm not sure which type of gear you mean by "maiko"-gear?

In general: The higher the ilvl of your gear, the better. A level 60 character can go a while in (augmented) shire-gear, I'd say til level 65/66 its still alright to be mostly in 270 augmented shire-gear. If you're not running the new SB-dungeons - and it sounds as if you arent close to that yet, since you havent finished the ARR-story, right? - it doesnt matter to much. Dungeons will synch your gear down anyways and for PvP your gear has no influence on the stats, its purely cosmetic at this point.

I'd recommend that you buy one full set of Garo-gear that you can then use to get a Garo-titel - doing Frontline and Feast-Matches while "wearing" this title will earn you achievments to unlock three special Garo-mounts. In the progress of getting those you'll see both Frontline and Feast and can judge yourself if you like either of them better (or at all).
For the moment I wouldnt exactly recommend trying them out - as far as I can tell from my own recent PvP-queuetime experience, everyone is doing Astralagos right now, so queues for the other content is basically dead. Personally I prefer healing Feast over Front and Astralagos so far.
A bit general speaking I'd say Astralagos is the middle ground between Feast and Front - in Feast you've got a smaller battleground and fewer people; Front is larger battelgrounds, more people (usually). Neither of them have mechs though - Feast tends to be faster and more engaged, while (depending on the map) Front can almost turn into a bit of PvE rather than PvP.

If you're really into PvP, you can ofc try to get a decent ranking in the current Feast-season!

Bottom-line:
- if you're only doing PvP, you dont need to worry about your gear
- get that shire-gear, so you'll be set for any dungeon until level 65, roughly
- get a Garo-title
- stick with Astralagos for the moment - personal recommendation, because of queues.