I used to do a lot of buying and selling, but have gotten away from it recently. However, with the upcoming 'guaranteed content' of colored Dbows, I think they are a good investment. I picked up 10 for 1.4mil and 10 for 1.1mil. I anticipate turning an excellent profit on these whenever that update comes out.
My most successful mechanting has always been centered around things I use to train my own skills. These tend to be the items I watch the closest anyway, and if prices turn south, I can always just use the items myself. For example, last summer I bought 200k pure ess to use (yeah, what was I thinking??) at 105ea, and then prices shot up to over 200ea. I sold, and turned a very nice profit. Later I bought 50k pure ess at 165ea, expecting it to peak again...it never did.
![Sad :(](./images/smilies/2.gif)
But I have used most of it in training RC, so it is really no loss.
If you are thinking of boosting your income by playing the GE, I suggest starting small and focusing on items you use. I have made good profits on pure ess, BGS's, coal, nats, and mith/addy bars.