Actually, that's a good idea. We should write some kind of community guide, especially since Squirtle is so complicated compared to some of the other PM characters. Problem is, all of the top Squirtle players either disagree with each other on most important points, or don't have the time to make a guide.
I'd be willing to do some kind of write up to serve as a starting point if people are interested, but I can't do it right now because I'm on my phone atm
I've been honestly trying to do this for years, every damn time I get started at some point I realize I still don't know enough about how to play the character and my guide would be pointless though...
there's SO MUCH TO CONSIDER when writing a squirtle guide, he's arguably the least straight forward character on how to play in the game.
On top of that, every squirtle plays really REALLY differently, so a guide would have to be written in committee to avoid being super biased and incomplete.
In general I say there are 4 steps to getting good at squirtle. And consequently 4 levels of squirtle players. Many are level 2, a few more are level 3, and only a very small few players I would consider lvl 4 if any.
1 - Stop being amish, learn shellshift, learn slingjump, not necesarilly being able to implement them super well, but just being able to execute them consistently, LEARN HYDROGRAB. Lean how to jump out at both the start and end of shellshift to get momentum boosts
2 - Find your inner luigi, wavedash A LOT, learn wavelanding onto platforms,
learn the invincible ledge dash REALLY well, I feel like all squirtles desperately need this technique, it turns the ledge into an advantageous position which is huge in so many matchups. Wavedashing out of shield, wavedashing different lengths, wavelanding out of Side-B hit, tech chasing with wavedashing. Learn zoning with bair and just general positioning with wavedash into shorthop/fullhop aerial to attack your opponent. Truly try and play the character like luigi
3 - find your inner capt falcon. Slingjump, A LOT. Learn slingjump wavedash (both directions out of slingjump), learn slingjump to offstage edgeguard (bair nair dair), learn short hop slingjump Dair crossup by using drift control to stop yourself in the air at a specific point to land in an advantageous position. Slingjump to reach platforms quickly, slingjump to followup out of throws, d-tilt into slingjump doublejump fair/nair/uair. Slinjump lets squirtle move quickly through the air, and increases his overall speed by a huge amount, arguably more than even his wavedash. To effectively use slingjump (creating space so you can do it, positioning accurately) is one of the biggest steps to becoming a high level squirtle.
4 - Now that you've learned movement, which is most of the character, you can start to work on finer points such as optimization, practice tech skill to cover distance as quickly as possible (allowing for longer combos), every grab starts turning into 0-deaths, tech chases become unstoppable, gimping becomes increasingly consistent, kill floaties off the top as soon as possible (80-110%), gimp spacies as soon as possible, kill midweights however you'd like. Aquajet like you're dirtboy, hydroplane U-smash like you're me, dunno what Dad does lmao.
just check this out, every level 4 squirtle should be capable of doing this (I would say I'm lvl 3+, not quite 4)
besides those main steps to being not terrible with squirtman, there are also basics that apply to every character like grab followups (D-throw is a DI trap with F-throw and U-throw), tech chasing on reaction, zoning (aerial watergun, grounded bubble, SHFFL Bair) so practice these from the start.
The goal to playing squirtle I feel is to with neutral by out-positioning your opponent, forcing an overextension, then getting a grab. Your throws can lead into tech chases or juggles that either lead offstage or go until death off the top. Every time the opponent escapes you go back to 1) NOT GETTING HIT and 2) making them think they can hit you (moving around). Since squirtle is so fast punishing a whiff should be something you can do from nearly anywhere onstage. Approaching directly with squirtle is BAD, you need to create openings since throwing out hitboxes as you move towards them is really dangerous. Hit and Run like pika, but when you do hit try and get a grab.