^ There's my guide to get from 1-37 for only 13k ish. You could expand the same methods for more magic experience, but it would get fairly slow. IF you are looking for cheap experience though, that's about the cheapest I can think of currently.
Just remember, it's all about efficiency and time management. If using a slow but cheap method takes 10 hours and you could use 6 hours of that 10 to make a ton of money and then use a fast expensive method to get more xp in the 4 left than you could in 10, do that. Ok that was a stupidly long sentence, basically make sure you are factoring in money-making time lost when using cheap slow methods. Sometimes the faster method IS the cheaper one due to the whole time=money aspect.
I am not sure what the price of law runes are but if you can mange to get some you could tele to camelot, but i would recommend high aleching right now