New player

Hi, just started off with 40k and Dark Eldar.

not really sure how competetive the DE is but i like the idea of the fast and unforgiving playstyle, havent played any games yet and barely got any minis, mainly spending time watching battle reports on youtube and trying to figure out how to build my army.
awkwardly waving from Denmark

The best advice I could give you for 40k is to read the rulebook forwards and backwards until you can recite it in your sleep. Ok maybe not that much but definately familiarize yourself with the rules because most armies are fairly competitive on a day to day basis but the general who knows the rules the best and how to use them to his advantage is usually the winner. Also dont give up when the going gets bleak. There have been many times I have pulled out a victory in the end even after 2/3 of my army is gone on turn 1 and 2.

Good luck and welcome.

The DE are fun to play.

I would say that if you pick one or two units you think are cool and three or four units that are good you will do just fine. The more you look at things on the internet the more you will end up with net lists witch can be a bit boring to play against (always remember to keep your opponent in mind.)