Proving grounds

It really depends of the team and the lead...

Some old teams seems to be interesting but aren't especially in the proving grounds such the team you confront.

I know you can find on reddit a post that list the team that works on this or that team

Sadly I don't have any GLs yet. Closest I am to one is SEE and that's only with tie bomber done.

I use Palpatine as lead with Vader, Imp Tie Pilot, Nihilus, and Sith Empire Trooper.

Sometimes, depending on if it's one of those squads that uses assists a lot, I'll swap Palpatine with Traya, then swap Pilot with Palpatine or sometimes Sith Assassin.

Oh, and BTW they are all maxed with the exception of Vader and Nihilus lead ability and all of their mods except for Traya, she's maxed to the max.

I probably made that confusing, I can give my ally code if you wanna see what I got as it's hard to explain.

What are the relic level ? 

But i think these squad aren't strong enough to succeed.

Check the trello below. It shows what teams work or not on each fight

https://trello.com/b/KbmP61P0/swgoh-proving-grounds

I think you must have at least one legend to be able to do it.

4 mil GP to open the events and R5 toons.

There's a website with several advices depending on the toons:
SWGOH Proving Grounds | Trello

You had to finish a complete 5 sectors in GC (but not sure having the red crave too) and to have a min MGP

Yeah maybe you have to finish at last a sector 5 but really not sure of this cause i had access to proving grounds when i was at easy difficulty.

And you DON'T have to obtain a GL before.

The trello speak by itself. And for exemple, i could have a 3* on Queen Amidala with a CLS team relic 3 (you just must have a good speed)