Doraemon was my first manga, I think. It was quite popular when I was a kid and the anime was airing on the local tv channels. XD
Then, there's Garfield for comics because the books previously belonged to my older brothers, I think. And of course, there were the newspaper strips.
I don't think anyone has mentioned Chinese comics but I used to enjoy "reading" Lao Fu Zi (a.k.a Old Master Q) even though I couldn't understand a word of Mandarin lol XD;;;; (I still can't read Mandarin. I've never read another chinese comic since.)
Then, my first manhwa was Ragnarok because I got addicted to Ragnarok Online, lol XD;;; (It opened my eyes that manga-styled comics do not have to be made to read from right-to-left.) Nowadays I'm following Noblesse and a few others which I haven't been keeping up.
As for webcomics... I'm a bit fuzzy about which was my first because I wasn't really into webcomics when I was in the weeaboo stages of my life, lol XD;;;;;;