Things certainly do change over time. I found that Iron Nuggets used to be rather lucrative, but with supply/demand going out of balance recently, prices have dropped by up to 50% as the markets are saturated. Now, I'm trying to smelt them in to Iron Ingots since there is more of a gap in that area on Figaro.

Use the item search feature before putting something up for sale. Check the current lowest price. You want to be within the top three on the list or your gear won't sell until everyone above you has sold their stuff and anyone else who comes along after you've put up for sale and undercut you. It's a cut-throat economy and you MUST undercut your competitors to move your stock.

Also, have a variety of things in your retainer's bazaar - the market system contains the possibility for impulse buying, which means you want to show off a variety of goods. Let people pick up a pair of canvas slops to go with their doublet while they're there for convenience's sake.

Don't bother trying to use your own bazaar to sell stuff unless you have a guaranteed sale. Too many players use their bazaar simply as an extra ten inventory slots by putting their selling-prices at an unaffordable maximum. This has meant that passers-by have stopped looking.
There is an exception - have something available for repair and you can have a chance of window-shoppers actually paying you attention (until said repair icon disappears).

Even a low-level crafter can make money. Higher level crafters will often not bother making lower-ranked things because there is no SP in it and they have enough money ongoing from other endeavors. Earlier in the game, I was making Tin Alembics because no one else was. If you can find a gap in the market, you may even get yourself a temporary monopoly.