Careful. Sounds like you're hovering on the edge of enlightenment.
Trading seems to me to be an exercise in Sturgeon's law.
After players get some experience under their belt, after the first game year, they run into immense difficulties trying to avoid building up ludicrous surpluses from dwarven industry. Clothing especially, if only in the form of worn out stuff. The common-most solutions are atom smashers and magma dumps. I prefer to unload absolutely everything unneeded on each and every caravan what rolls in. All I trade for is an occasionally vital item here, an occasional oddball item there, or to keep up the variety in food an drink, and grabbing every steel item for melting down for manufacturing and armor-smith training. After dealing with me these traders are well on the way to becoming billionaires in a world where having merely $1,000 would be considered outrageously wealthy.
Sudden unreasonable export bans being what they are lets you live life on the edge with the justice system as an added plus. But, usually, after a few years, you can manage all your trade safely on worn out clothing alone.
Before the first year you might run into a jam the traders can fix if your trading dwarf is skilled enough to entice them with your limited resources. Like, if you started without an anvil or something. After two years or so you can conduct trade with the most incompetent dwarf on hand and obtain everything you need (maybe not everything you want, though).
Save when recovering from a disaster, I've never had an issues with a lack of immigrants. Most newer players want to quickly get their head around the soft and hard population caps, not how to speed new arrivals.
Would be nice if the elves sent more wood, but that depends on how much wood you have stockpiled at the point of their arrival. Previous profits have only an indirect connection to wood-bringing. There are a myriad of other trading stock relationships un-/barely connected to trader profitability.
Does skill, or reputation matter? For most players giving them extra stuff, making them billionaires, is as pointless as being masterfully miserly.