Destruction army help

[TheBlackHood157]

So, my first army was a destruction one. I havent used it in a while, and i feel like playing a game against a friend, so were playing 640 points, but i only have 520.. i play mainly greenskinz and moonclan. My list so far is this:
Orruk Warboss
20 grots
10 grots
10 orruks
3 fanatics

[Warboss Gorbolg]

I don't have a ton of experience but I struggled with 20 strong Moonclan units, even at low points levels.  I also don't believe that 10 man units of Grots are legal.

If you're looking to grow the force, I think Fellwater Troggoths are worth considering.  Look great and give you an elite unit.  A Moonclan Shaman would also be worth considering for expanding your force.

[Sheriff]

With units of 20 grots the trick is to be cowardly. Don't attack things head-on. Just try and survive whilst just netting threats. 

What you need with moonclan or as mixed moon/spiders is something to protect with the grots. Eg spider riders, arachnarok, mangler, squigs etc. You need something killy to throw at the enemy armored units (moonclan) or to flank and gank (spiders). 

The alternative is to solve the squishy grot problem by simply doubling down and getting way more grots - they get way braver and higher damage and survivable in bigger units. Then get a shaman to buff them and they turn into right little killers.