I already Bought, BTC, ETH, NEBL, (75K$) Now I want to invest 10K $ More, What to BUY?
That's a pretty big investment already, congratulations.
I would definitely try to diversify my portfolio into more coins, if I were you. 3 coins is probably a little bit less than what I'd expect for a normal, profitable crypto portfolio. Perhaps sell off some ETH while it's still hot for other mid to lower cap coins.
For your $10k investment, to me, I'd definitely invest them all in XMR if I can.
The price of XMR hasn't really jumped at all despite the entire crypto market just exploding in recent days, so you can be sure that it's undervalued. Also, long term wise, I can really see XMR's privacy being appreciated more and more.