you can still mine xcash or buy on exchanges
I would recommend
https://trade.citex.co.kr/trade/XCASH_ETH
https://app.stex.com/en/basic-trade/pair/LTC/XCASH/240
https://app.stex.com/en/basic-trade/pair/ETH/XCASH/240

but were also on hotbit and graviex

There are only going to be 50 nodes, but 45 only since we are having 5 seed nodes(they wont mine any blocks though)
as for the amount its a total guess right now

you can view the current delegates in a beta test at
http://delegates.xcash.foundation/

if you look at the average delegate total vote that would be the amount right now to get into the top 45 for this test

I assume mainnet will be much higher, but it totally depends on who stakes and who shows up

we have estimated in an article it will be around 540M but it could be lower or higher