I usually can find a hint 3 from 4 runs, so I usually do it before another run in hopes of becoming another. I will usual get my killcount to approximately 125 at the RS gold time of 1 jog, which gets me about 325k profit.
You would like to merch items which have a steady fluctuation, if this is reasonable. Something which rises and falls, but . To see when things will rise or fall outside of the cycle, check for big updates like double xp weekends or fresh quests. Attempt to merch items that alot of individuals use for skilling, and also do it in bulk.
When buying on the market, I usually go approximately 5%-10% lower than moderate price. You can then sell it once the price rises for 5%-10% above, or you can come up with your own"wholesale" cost, which will generally draw more focus from selling beyond the g.e.
If something doesn't buy/sell right away, do not be worried. If it does not purchase, it is because you are buying under moderate price, and only people who don't care/are desperate for money sell under medium. Normally, the thing will buy by the end of the day. If it does not sell, possibly it is a product that's not in high demand, which means you've picked a poor item, or the price you've set is too high. I would not recommend taking down the price before a day or 2 after you have set the offer up. Remember, merching does not happen over night; it take alot of patience.
I would advise purchasing everything on the g.e.. If you're using raw materials like raw fish, logs, herbs, etc. I would sell on the street for a set price per item. If you are selling anything else (essentially non-skilling things ) then I would say sell it around the g.e.. It could take some time, but this really is the best you can do, as it's harder to buy OSRS gold find someone looking for ten monster platelegs than 2k nature runes.