Noob here, try to be nice! I'm just starting to consider getting into MTG, but have some concerns...

I'm a 43 year old guy and my fiance recently passed away so I'm looking for a community to join to help me move on and maybe make a friend or two. That's not the focus of this post though. I've been trying to read up on how the game works, and I keep seeing that proxy cards are either: the best way to learn by building custom decks OR proxy cards are ruining the game. I looked at the price difference between the power 9 cards on eBay and on AliExpress, (my source for Kayou cards)and the costs are astronomically different. I'm hoping the cards say PROXY on them or something, because as I slowly gather cards I don't want to intermingle real with proxy by accident and get banned from whichever lcs I join. Do I need to mark the proxies myself or are they obviously fake the way Pokemon cards are fake? I'm just trying to do things the right way, but I can't learn on the budget it would take to get most heavy hitting cards from real wotc printers. See I'm learning a little already!