You'll need to buy an ASIC, even with the most powerful GPUs today, you'll earn dust and negative profit. Heck, you'll probably wear the GPU out. Poor thing! For GPUs, try Ether, or if you'd like to buy an ASIC, try the S9. I suggest the S7-LN from Bitmain if you have cheap electricity- they're amazingly cheap and run pretty well for a beginner. Also ships with its own PSU, which you'll need for most all miners, but if you do buy it, replace the PSU. Lots of reports of 'em burning out recently. S3s are reliable miners as well and will only cost you about 65$ if you like learning, but overall, if you need profit, buy the S9.
We really need to know OP's electricity rate. So hard to tell people what do on asic's without it at this point, just ROI is all over the board. One thing to keep in mind even if you achieve the 50 to 100 USD per month that over time it goes down. We can only speculate how fast it will happen, but it will go down.
On GPU you still go into it spending a decent amount. It takes a decent GPU and most likely a open air system that you make. You just don't see near as many miners using cases as it is so much easier to cool down with open air. I do mine both Ether with GPU's and BTC with asic's. I can say the asic's are kinda dummy proof at this point. I find putting together a nice system with 5-6 card's to take more technical skill, and more tinkering most likely. And yes that is just at start of GPU system this extra effort for the most part.
