Hey there. Firstly I wanna point out that I am mainly just knowledgeable about ICs, I'm not a top player by any means, so take any advice I give about top level play with a grain of salt haha. But anyway, in my experience sticking with ICs is all about character dedication. They're a very high maintenance character, you need to know a lot, you need to practice tech a lot constantly, so I think just genuinely liking the character for what they are goes a long way to staying motivated on that road. For me it was the fact that their entire design was both unique and almost infinitely interesting. Unlike any other character they have crazy dynamics everywhere, so there's always something to refine or learn. If you want to win that badly then you might be able to get away without just liking the character, but I think it helps a lot. So, whether or not it's worth it to you I think depends on how willing you are to put in the work. If you put in the time they will reward you with great matchups across the board, and a huge fear aspect (CGs!!!), so it's really up to you if the constant maintenance is worth that. There are a lot of other characters you can do better with sooner, but there are only a few that you can do better with once you're at the top of the metagame. I think "just liking the character" also factors into this too.
As for tips, the main one I think is to just make sure you're on top of CGs. Practice daily, you don't need to practice every single character in the game (at first, anyway), but have a rotation of characters that you go through weekly and practice CGs on a few characters every day. Seriously, practice this before even desynching or "playing well". Knowing when and why and what to desync takes experience and matchup knowledge, and just playing a lot will develop your fundamentals naturally. But CGs are the active work component that will always be there. At first you WILL get grabs by accident even if you're not good at desynching or whatever, so make sure you fingers know how to go to work when this happens. Also, use the F/B CG and make it a secondary goal to learn to do it as quickly as possible. It's unmashable, untrippable, works on platforms, requires no space and works on everyone, so yeah, learn it now and reap the rewards.
(Side note: it's unbelievably hard on Lucas though, so consider something else for him lol.)
To do well at a national level it's basically required that you never mess up CGs on anyone, ever. You can, and some do (eg 9B), do well with good CGs and little to no desync game, it's just that important. However at national level things like desync knowledge, great fundamentals, reading the mind and habits of your opponent, great character knowledge (in particular knowing what Nana will do in every possible situation, and being able to judge obscure things like whether your SoPo is able to solo CG a character given an arbitrary percentage and dthrow staleness), knowing how to setup grabs efficiently and knowing matchups well all become a lot more important for your ability to excel. It's a lot of stuff, but the good news is you will naturally develop a sense for most of those given a lot of playtime and some active problem solving along the way. Of course, there is a lot of information floating around the ICs board that can help tremendously with this process too.
So yeah, sorry for the text wall, and I hope all that work doesn't put you off, but I think I did a decent-enough job of covering everything. If you need any further advice or clarification, feel free to contact me anytime. It's always good to see new enthusiastic players of this character.