Well, first, it should not be a question if you can invest bitcoin in 2018. Here are some helpful tips that I think you can consider:
1. Of course thinking of investing one must have sufficient fund to invest.
2. Don't give all your money to just one investment, no matter how good it looks. Learn to spread your treasure, for security purposes.
3. Make sure that you will not include your life and your soul in your investment. That when you loose with your investment you also lose your life.
4. Be a smart saver, smart spender, and smart investor.
5. Read and search a lot before investing. Knw the in and outs of the business.
6. Don't give out what you can't loose.

I hope that helps.