My question is if it's still worth buying Asic's and start mining BTC in 2018.
If not mine BTC what other coin is it worth to mine nowadays?
it's still worth it to mine BTC. Why? Because that is the main source of BTC. You can mine BTC while investing them to long term trading systems. Don' t invest it on HYIP or Ponzi Websites. You can also earn some BTC in Gambling sites as well. But the best thing is to mine BTC on your own.