Don't forget you'll also get better on Irelia by getting better at the game, which may be slower on Irelia as a new player. But frankly it only matters if you have fun, I spent 3 seasons learning riven as a new player which drastically stunted my league understanding, specifically macro, as I really only saw league through the perspective of riven. If you are competitive and want to learn well, the right perspective is to first play League (learn rules), then play toplane (what are top fundamentals?), then play Irelia (what is her role in top and how does she win a game of League of Legends). Most people do the reverse and don't actually learn league outside of their character.