Hello guys. I want to play with a pick, because so bassist that inspires me plays with a pick. And i couldnt decide which thickness it should have. So, would you give me advice? Thank you.
It's entirely personal preference.
If you want more "snap" to the sound, go thinner / if you want more thud, go thicker.
If you want a more responsive feel, use Nylon / if you want greater stiffness, use Delrin.
Whilst Delrin has more "clack", and Nylon has a softer attack, those things effectively disappear in a mix; the "snap" or "thud" provided by the thickness has the greater impact (particularly when you factor in compression, and EQ).
If you want a middle ground between Nylon, and Delrin, and with improved grip (if you suffer from sweaty fingers), look at Tortex, and Gator Grip.
For extreme ends of the spectrum, there's Metal (super bright and clanky), and Felt (more like sausage fingers).
My personal favourites are the D'Andrea / Planet Waves 1mm Delrin picks, but I almost never use them (except for sometime when recording), because the Dunlop 0.88mm Nylon pick sounds pretty close, but has far better responsiveness - and in a mix, the differences disappear.
TLDR : Dunlop 0.88mm Nylon.