Woo you got a 50, very nice.
My tips:
1. Get rid of resistance gems, go with dex
2. Cluster on helm/boots (can do MS as well, check if you get items that give +Fire/Cold, if cold then go CA, fire go MS)
3. Get sentry closer to 15x3
4. Better bracers, easy one is the Reaper's Wraps craftables
5. Better belt, Sherma is ok while you're shooting, but there are several better ones
6. Better sack
7. Get a hellfire neck
8. When getting new items, pretty much always roll max damage
9. Multishot->Arsenal so it also shoots rockets for your ballistics
10. Sentry->Spitfire
11. After that check how many times you have all the sentries out in a GR; if not a lot them take e.g. Steady Aim > Engineering
12. Make sure you're just on a BP (e.g. if you're in the middle to the next 1 then you have wasted +attack speed)
13. For followers, check if you need the Enchantress +3% attack speed to get to a BP, else go Templar for the extra heals
14. Overall you can drop a lot of toughness etc for extra damage. If you can hit 1m damage you're going to do a lot bigger GR. Doing 35/36, if I have 6m toughness white trash can almost 1 shot me. If I want to go higher I have to drop toughness a LOT for the extra bit of damage (and then not get hit)