The comment from GiantTree is correct, however I am answering here so the question can be closed and to give a more specific answer.  Trade up Contracts give out skins based on what skins you put in.  The output skin is both one grade higher than the inputs (Industrial will give you a Mil-Spec, Mil-Spec will give you Restricted, etc) and must be from one of the collections of the skins input.

For example, you could put in 5 Glock 18 Catacomb skins and 5 AK-47 Elite Build skins.  Both of those skins are Industrial Grade skins, Catacombs is from the Chroma collection and Elite Build is from the Chroma 2 collection.  Thus, you can get out of it any Mil-Spec skin from either Chroma or Chroma 2 (namely, Dual Berettas Urban Shock, Desert Eagle Naga, MAC-10 Malachite, Sawed-Off Serenity, AWP Worm God, MAG-7 Heat, CZ75-Auto Pole Position, UMP-45 Grand Prix).

Most of this information is available on the wiki plus additional information regarding exclusions and exceptions.

How do people know what they can get out of trade up contracts?
So i am trying to start investing periodically some small amounts.
I am particularly interested in index funds or ETF.

I would like to be able buy, track, sell them, and etc online.
There are a lot of online brokers like : TD Ameritrade, etrade and etc. , but i cant seem to find the one that would allow to register fro Europe citizen, like from Denmark. (all the top ones require USA citizenship or etc).

Is there any like that at all ? If not - what other options there are to make such investments ?
