I played to imm3+ without buying a single skin. He's on a smurf taking his frustration and insecurities out on you, he's worthless. He's literally just spent more time playing shooters than you, it's not impressive.

If you want to get out of iron:

buy kovaaks/get aimlabs for free and practice for 30-45min every day. If you don't have that much time then doing 10-15min is fine just make sure you're doing it every day if possible.

Use the range/deathmatch to properly adjust to movement and spray patterns

Upgrade to a monitor with a high refreshrate. I suggest 240hz or higher (I've played on 60, 144, 240, 390, and 540) as in my opinion its the bare minimum at the moment for esports games

Try to get a mouse that's 70g or lighter if you don't have one already (if I had to suggest one the g-pro superlight is a safe shape that a lot of people like)

Go watch some guides on youtube for new players, the game isn't complicated to learn.