If you want to try bitcoin mining then don't even try to buy and start to mine before halving. We have no idea what what exactly will happen with mining after block reward drop.
Difficulty could go down because people will cease to mine, or it will quite the opposite because it will be profitable because price of BTC might be higher.
In short: Wait and see.
I think we need to wait till the halving occurs, as we don't know what will be the exact scenario at the time of halving but this would be definitely the best year for bitcoin.
Waiting is recommended not only because of the halving. Certainly in short time, will be released S9, then after halving and with new rig will be good moment to start.
