What are the fastest, semi-cost efficient methods of training magic?

High Alching or making emerald rings.

I told myself a long time ago that I'd never alch again for exp. I will hold to that.

I think plank make is fairly profitable and 140k xp/hour.

 

Of course you could fire surge enemies for roughly 150k/hour and profit depending on the monster, alch inbetween casts for 200k+/hour

Which log is generally used for plank make?

High Alching or making emerald rings.

Alching is ancient, inefficient and an all round bad way of training magic.

 

You should be looking at Plankmake (at times you can profit, usually the loss is minimal though), Stringing is pretty good too. I've heard Hunterkit is decent too. Then you can always try Stun-Alching. All of these methods are 120k+/h with relatively small losses. Nothing that can't be made up for by a few hour's of boss hunting.

Burst then barage skelles. you can make up the cash with the time you save