https://yourbitcoinpharmacy.com is one of the cheapest pharmacies I used. They accept BTC and carry wide range of medicines

I don't think investing is a good idea. When we talk over non-stable currency, you basically have 2 options - buy and sell. Investing should be done with a stable currency  (usd, jpy, gbp, e't'c')

Sure possible, all major exchanges don't take any commission, so just store your btc there