Level 78 Store Items

Hello, I need a bit of recommendation as I'm new to the game.
I have like 25 points and I'm looking to buy a item from the store but I'm level 78 with no interest in leveling to 80 currently.
I don't see much items available for purchase if you're not level 80, why so?
Can you recommend me some items from the store(if any) for level 78 with points, currently I'm 2.7 GS so I need good ones(if any).

Also can you tell me where I can obtain best level 78 items in game(like dungeons,reputations,anything that gives best gear for the level.)
Only interested in agility and stamina items(cloth and leather).