Guild stores are for people. You need to go to the merchants. Like the ones at crafting stations

Just checked it says "no permission. The Guild must have 50 members to post to the Guil dstore)"

Hello

You can find merchants all over the game. All towns/cities and as someone said at all crafting stations, the most useful are those merchants found wondering the roads. Sell your trash at these and repair if you do not have repair kits. Long term I do find the merchant bought for 5000 gold in the crown store very useful - but she does not repair.

It is worthwhile keeping all glyphs and intricate items for deconstruction later to improve your crafting skills on any alt you have.

Now - valuable items you find. How do you know what is valuable? Generally items below CP160 you can safely sell to merchants or deconstruct for crafting XP and materials. Usually CP160 sharp or maybe infused set weapons have value, and divines/infused/impenetrable for armour sets. CP160 crafting materials and alchemy materials do sell well. Fishing can be profitable - albeit slowly. If you look online for tamrieltradecentre you can search for most stuff and see a price for what other players are listing in guild stores. Note these are asking price - not necessarily selling price.

Guilds and Guild Stores for selling stuff - a lot have no requirement for minimum sales and others have a fee if you do not sell enough. I'm in several with no fee and it works well. Ask on-line - looking for trading guild, and check their requirements. Small Guilds will not usually have a Guild Trader - traders shown on your map which they rent in game. In small Guilds you can only sell to other Guild members. Try to find large Guilds - say 300+ members that has a Guild Trader. Once you are in a guild use Master Merchant or similar add-on to give a guide to selling prices. I like being in Guilds - not just for selling.

Good luck and happy selling.