I'm looking for a good seedbox that doesn't require to download one files at a time. The seedbox I used is cheap but it sucks because I have to download files one at a time not all at once >.>

A seedbox without a web interface is just a server mate, it doesn't really become a seedbox until you install a webUI (rutorrent front end)
What you want is auto downloading, you can setup a seedbox to grab certain content on a tracker without you having to feed torrents into the seedbox one by one, you can set this up manually with each tracker or there are some scripts to help you do it.
I've never actually done it myself so another member may help you with this, I enjoy adding the torrents.

One more thing, a cheap seedbox will always be that, CHEAP
You can't expect miracles from something you paid so little for.