Making gil is still possible.
For DOL materials, look for items that sell in excess of shard costs. Shard costs are your threshhold for what is trash and what may be worth time to sell. Keep an eye on sale histories to get an idea of how much is selling per hour/day, in what quantities, at what average cost. If an item is selling at 25 gil or up, it may well be worth the trouble to put something up for sale (around 2.5k for a stack). Don't put up more than one stack of an item up per day, or you will create an artificial ceiling and crash the market.
For DOH goods, level 50 two star items are a 'one a week' sale. There are a lot of high-end crafters, and you can expect anywhere from 0-4 items to sell per day total. Fierce or aggressive competition will only cost you a lot of gil trying to undercut one another. Items that tend to sell better are HQ items used to turn in leves for lazy crafters seeking to pay their way to L50. There a healthy variety of items to be made, and if you price reasonably, you can cut a fair profit while putting out prices that lure prospective buyers to take that route. Remember, you want it to make it worth not just your while, but theirs as well.
Most of the rest, particularly low value 'trash' and low value items in small quantities, are probably best vendorized or otherwise taken out of circulation. High value items, of course, by all means, toss them on the market; eg two-star philo ingredients, maps or TH drops, and rare dungeon drops such as Fine Wax or Amdapori stones.