Hello all,
I am looking for mainstream display/native/mobile traffic in every European country.
Eastern countries are even better than Western, but our company buys traffic in whole Europe.
If you could recommend some networks, companies that would be awesome.
Maybe some companies has representatives on STM and can PM me.
Thanks for help
Adult or mainstream traffic?
Only mainstream 
We sell dietary supplements, which we manufacture, you know the drill. Diet, skin, muscles, male enhacement... 
Since you're the manufacturer, you should definitely consider working with some affiliate networks too, did you consider taking this route at all?
Then there are the obvious matches for whitehat promo methods : facebook, adwords, bing ...
Next come native networks : revcontent, content.ad, mgid, taboola, outbrain ...
For male enhancement, you will have to take this to adult sources anyways - try trafficjunky, exoclick, trafficstars, traffic factory ... or pops from clickadu for example ... members area traffic maybe? Adnium, greenpoint...
In case you have proven funnels and can work with mobile traffic with higher bids, how about some mDSPs - go2mobi, avazu mdsp
Last choice would be POP traffic - properller, adcash, popcash, popads, zeropark ...
Also make some research about email traffic, properly targeted lists can convert like a charm.
These were just general answers, I guess you knew about half of them ... but hopefully I gave you an idea or two anyways 
Hi,
We have Premium, HQ traffic in all European GEO's .
www.adoptim.com
do you work on self-serve?
We are CPV/CPV.
Welcome to mail me: katya@adoptim.com
(our platform is mainstream)
Best regards!
we're an entertainment advertising network.
Hi koolfashion,
We work with both mainstream and adult traffic, very competitive bids and worldwide coverage for both banner and pop creatives. You can run both desktop or mobile campaigns.
We also offer a self-serve dashboard AND managed account who will optimize with you to meet your KPIs.
www.ezmob.com
Hi koolfashion,
ActiveRevenue works with mainstream and has huge amount of exclusive direct traffic in EU. PM me on Skype for more - boris.adventurefeeds
veeseo, plista and lockerdome are some other, lesser known ad nets you might want to try out
Hey buddy.I am representing an Adnetwork with native CPC/CPM traffic in ALL EU including the surroundings and the East Europe.Please add me on skype at andrei_adnow for more details