It depends on the item(s). If it's something I know I can't get, I'll trade for it. And if the item is easily/ or slightly difficult to obtain, I'll get myself
When I need something, I'll usually try to trade for it. If I can't find what I'm looking for in Re-Tail, I'll either wait until I can trade for it or until I manage to get it in-game, whichever comes first.
I had no idea this forum existed or that you could trade/sell in-game items at all for almost a year. The first thing I wanted was the entire Rococo set, and I got it by ordering the items from HH Showcase homes I Streetpassed at airports. This is still my favorite way of getting items.
It took me a year to get all the fossils for my museum and I did that by digging in my own town.
It depends what the item is, if its an item I can easily get I'll get it but if its not I'll add it to my wishlist and see if anyone has the item like amiibo items
if they are in game items I try to reach them myself and only when it's really hard I ask to others (the snowtyke ones were impossible for me)
but if there are items related to outside things like region dlc or amiibo items I trade for them without hesitation