New shopper here. How do I become more consistent in actually being able to buy I want to buy?

New to Marketplace but not Facebook, and plan to use it as a buyer more than as a seller. I live in a city and mostly rely on walking and public transportation to get around.

What I'm still getting used to is the transaction process. Since it's not regular online shopping nothing is locked in until you meet in person and make the purchase there. At least 5 items I found something that I'm interested in purchasing and so far I've not been successful in buying them. Either the seller does not reply, or they do, but then don't reply again for many hours on follow-ups for meeting, only to suddenly be notified that the sale is done (someone else had paid).

How to get my purchase average up? I know this sounds like a strange question to ask to regular sellers and buyers. When there's items with several interested buyers it always feels like a race to get there first, but I don't just want to show up in the general area without follow-up because that wouldn't be polite and I'd feel stupid if I showed up and the seller wasn't around.

Sellers have a problem with no shows. As a buyer, I seem to have a problem of "too slow".