Well, the prices people are listing in here are ridiculous.. You can easily buy gold for .5, anything above .5 is a rip-off. If you had bought the gold 2 weeks ago you could have easily gotten it for .4..
But if you do buy gold, you won't be able to enjoy the amount you have nor will you be able to invest it, or make more money with your gold easily, which does become easy if you have enough to invest, box, or dice host with, whatever you choose to do. Wasting it on prayer and herb will be getting rid of your money right there, just get items and other things you want and finish maxing your account, get prayer and herb off legiting in the game or over time.
If you can make double the money you buy, which isn't too hard then you can spend that on the prayer/herb, otherwise I just don't see it worth it.