Your ping will be the same, as it is your internet and where your located that counts. You should go to the hardware and support section, make a threadl inking to the computers you like the best, and then ask for the best computer that is under $400.
Main aspects for a good Gaming PC would be decent graphics card (google the model, or check amazon for the quality and rating + info), and decent processor. (again, find out the info on the component).
A decent amount of RAM is also important, you don't need loads, just enough for a smooth running PC able to spread out a bit of workload.
The best option would be to make a custom PC if you want to save money and make it specifically for you..(gaming).
But as Hero mentioned, post your question in the right section and you'll find better answers.
"Depending on the context, I may or may not enjoy getting stoned to death" - zιтнιυм