ICs first tourney? I'd recommend you have at least
- One fast desynch you can do stuff with to avoid people using the Luigi strat vs you (not sidestep, roll, etc. - more like DD desynch or the turn around f-tilt one; just something not so telegraphed so you can do bizarre things to get out of people trying to limit you with positioning)
- Control over WD lengths and some basic fluid movement with dash & walk in and out of WD
- Competence with their basic CGs vs CGable or semi-CGable chars (Sheik, Fox, Ganon, Falcon, Falco)
- Competence with handoff vs the characters you damage race hardest (and where there's no guaranteed CG to build damage - Fox, Falco, Peach, Marth, and Puff are the main ones I'm thinking)
- WD OOS, the shield size tricks, and some knowledge of their OOS game aside from grab (they're different backwards than forwards vs a lot of chars)
That's about it
After that just add what you think you need to shape a good style. ICs afford a lot of variance in how they're played.