I'd advise you to not go with a VPS provider simply because they are cheap because with most companies who sell their servers for a lower price, most of the time, oversell the nodes and therefore the power and resources of your VPS are shared among others. Go with a reputable company over one who is cheaper always, such as photon vps, I have used them a lot in the past and never had any issues when running large scale bot farms. The company KMJT mentioned will also be reputable.
Also you need to remember not every provider will allow you to use their servers to bot on, runescape clients use a lot of resources and most companies won't allow them so make sure you are able to before paying for anything.