I'd buy several different picks and see which one worked the best for me. No need to purchase the expensive ones unless you just really want to.

I use a Martin pick on my Martin now, but for years I just used whatever pick happened to be available and most seemed to work. I found for me, that I needed a lighter weight pick but you may need a more heavy pick.

It's really a personal thing for each person.

I tend to agree with Texasbanjo that it is pretty much personal preference. As for me, I tend to alternate between mediums and heavy's, depending on how my 69 year old fingers feel that day. I also agree with you Ellis, I'm not dumping that money into a Blue Chip guitar pick.

I have tried dozens and dozens of picks, the best is hands down tortoise shell. The only thing I would settle for is casein CT style or a bone pick that I make myself. I am one of the few who hate bluechip.

Juan Solo

Normally, I prefer something around 1.3 mm but this material is stiffer than any other plastic, so 1 mm works perfectly for me.
Don't get me wrong, it's still some sort of plastic - they call it synthetic bone/synthetic tusk, "Tusq". The point of it is, it's harmonically identical to bone, totally efficient in terms of resonance. You might notice they are super inexpensive too.
Growing up, I used a "Golden Gate" equilateral pick because that's what my Dad uses. He punches dimples in his, because they are slicker than snot. These GraphTech TUSQ picks are easy to grip, and there's no flex or "give" in them whatsoever. I simply place a Golden Gate pick on top of my bi-angle blanks and trace it with a pencil, then use a nail file to trim to size.

This material withers away very slowly, so... over time, you'll need to flip it and use the other side, and eventually you'll need to replace the pick.

BUT AT LEAST THEY ARE NOT $50! DON'T FALL FOR THE HYPE OF THOSE "BLUE CHIP" PICKS, THEY ARE PLASTIC.

When you drop a blue chip pick or any mainstream pick, you hear a flat clicking sound. When you drop an ivoroid bone pick or one of these TUSQ picks, you hear a chime sound. The best part is the feedback you receive when you attack the strings!

I prefer this same material for nut, saddle, and bridge pins as well. It makes ALL the difference! Your guitar will sing loudly with these parts installed! I had some junker guitars before, and people bragged on how great they sounded 

https://www.sweetwater.com/store/detail/PQP0400BA--graph-tech-pqp-0400-ba-tusq-bi-angle-picks-4-pack-mixed