You'd be fine with a 550W with everything at stock. If you're gonna OC and are thinking you may upgrade your GPU down the road I'd just spring a few bucks now and get a 750W minimum now. Getting in to the 850W range is nice if you want that 2nd CPU connector or just need more connectors, or if SLI of two low end cards is in your future.
The 1050ti barely uses any juice, and your GPU is your primary power concern. When you start getting in to 1080s and 1080ti's you start talking about 400W required JUST for the GPU.
In regards to what actual GPU to get, an 80+ gold rated is always recommended to ensure you're actually getting as much actually wattage out of it as you can. A gold rated PSU should be around 90% efficient, so with a...