>> I do not want to send too little and people think I skimp on trades. What is deemed a proper amount?
I think the only solid answer is to tell them up front how big your packets are, then they know ahead of time.
In one big swap where it's common to trade fairly unusual or rare seeds, "20 seeds is enough".
I always look at 20 dust-sized seeds and think it is not very much, but if they all germinate, it is plenty. Sometimes really skilled gardeners will boast that they "only need a few seeds".
I go partly by how rare or expensive the seeds were. If I buy a big enough packet, I can split it up many ways.
If you collect the seeds, all you have are all you have. After you set aside what you want to archive or sow yourself, decide how many trade packets you would LIKE to make. If you look at them afterwards and feel ungenerous, reduce the number of packets until you feel generous.
But for common, commercially available vegetables or flowers, if the cost to me, divided by the number of packets I make, falls below 50 cents or so, I tell myself to put more in. For rare seeds, I might hope that the recipient will multiply them. But for common annual seeds, it is nice to give enough that they can just PLANT them, and not have to multiply them before they have a nice stand.
But now I find I would rather give seeds away than trade for them. Sometimes I get distracted or lose things, and forget to send them. Better to NOT have someone waiting and cursing while I go off into the Twilight Zone.
I tried to trade or give away Asian Brassica seeds here for a while, then gave up. No takers. I think that a lot of people here have been gardening so long that they already have everything they want, except for very specific and often rare cultivars. That's just my guess.
Unfortunately, this year Ella's "Hog Wild Piggy Swap" in Cubits needs to take a break. Otherwise I would steer you there, for an annual event that's quite an event.