awesome run!!!!!

Hello! I have been watching speedrunning from the sidelines for a very long time and wanted this game to be the product of my first speedrun. However, I have never done any sort of speedrun before besides doing some attempts on mario kart 8 where I wanted to be a rainbow road runner (I wasn't very successful ( ' ._.) ). Any advice on what to do first? I've already completed the game and I'm attempting to do my very own 100% completion (not a run) as of right now. I have seen numerous videos by Linkus7 and PointCrow but I'm wondering if maybe this isn't the game I should start on. Any and all advice is highly appreciated!