When using a VPS you have to make a tradeoff between the price and the latency it offers between your MT4 application and your broker's server.
The signals must be realized as quickly as possible. With high latency your entry level can be far from the optimal one. It will give you different trading results.
Ideally a VPS would give you a latency of under 10ms. That is what most forex optimized brokers brag about, but also the price is higher.
A "normal" VPS which comes free or it is cheaper, can be slower, but if you choose its location closer to the broker's server, you may be able to have a workable latency (under 40ms).