Great question! Thanks for asking :) First, I'll say I think the definition of meme is fairly universal.
https://en.m.wikipedia.org/wiki/Meme
Memes get passed around on the internet.
Next I'll say it's my opinion there isn't a clear definition of what a repost is. Repost means different things to different people. During my time here I have seen a spectrum of opinions, (not actual quotes, some quote marks are for reading ease) from "I used that image for a meme once, so you can't use it and every meme that uses that image is a repost" to "my meme had that caption, so you can't use anything close to my caption" to "I saw that once on the internet, so it's a repost" to the more realistic (actual quote here) "The whole point of making memes is to get them reposted. That's the point of making a meme. Reposts are foundational to what memes are. If your meme has not been reposted yet, it's not yet even a meme."
Next, I'd like to say it's my opinion its impossible for you repost something of your own creation. I call those resubmissions.
Ask a hundred different users what a repost is, you are likely to get some variation in the answer. I've noticed a lot of people who will call repost have said things like "I don't have time to explain what a repost is" "I'm done talking about this with you" Sometimes they have actually posted stuff on imgflip that meets their definition of repost. Talk about hypocracy!
What your definition of a repost is and how or when you do it and how you conduct yourself is up to you. There is a Conduct section in the
imgflip.com/terms
There is a comment on an old meme from back when I was a noob that completely reflects my philosophy on reposts. " ...there's nothing that I like better than to see people repost my memes or post my comments as memes. It's the highest form of respect possible on a meme site, and I wouldn't want anyone to discourage people from doing that."
Help yourself to any of my comments or creations if you like. Hope this all helps you with your own position and style. I like alot of imgflippers, some only make original content, some are a mix of "reposts" and original content, a few who say they are 100 percent "repost".
PS, I'm not sure who is a bigger fan of doMima, me or you :)
Caption this Meme
