Dunno mining with alts? then selling the gemss / Steel, fastest way buy a printer Like gpp BDP or somthing then go base with people or buy somthing cheap "or normal priced" then sell it for a bit higher in your shop as shop owner or make 30m Cointflip 50/50 Chance or u lose it or u double it.
Edit: If you are gonna cointflip do it the smart way start of with 5m if you lose do it again but this time for 10m then if you win u will get your money back then restart at 5m till u make enough profit then u stop.