It is, surprisingly, at your bank. when you open your bank there will be three tabs at the bottom; bank, reagent bank and warband bank. Mind you, it cost som gold to open both of the latter options. But no more than you can have as f2p .
Adding sockets to neck is doable. Amnesia f.ex is easy to get to use for sockets. This is tested on f2p L20 character. Agi and int gems from mark of honor is +4 at 20, so thats a nice +12 main stat on top of necks own inherent stats.