I tried picking up sazabi and i had a lot of trouble. the first thing to do is understand his most powerful technique, the achakyan. if you don't use it you can't win, it's that simple. any time i fight a sazabi and see he's not using it i stop worrying because the suit is only at 50% power without it.
Achakyan
https://www.youtube.com/watch?v=yml0Un6o_N0
this video shows what it looks like when you do it right (starting at about the :30 second mark).
basically, when you have a stock of BC, you input a 6b then rainbowstep it and as soon as you hit the second input to finish the step you do BC canceled into CSa. the Csa timing is tight - about 2 frames - and if you didn't do the BC fast enough after the step it won't work either. you'll know you've messed it up if...
A.) the BC assist is summoned
B.) you get stuck in the air firing shotgun
if A) happens then your CSa timing was too slow. if B) happens then you either failed the BC input or you just weren't fast enough after inputting the step and you lost momentum.
note that if your BC is at 0 or the assist is active you can't do this.
you can do warm ups by just doing BC->CSa on the ground. if sazabi crouches a bit on the ground and says his special BC dialogue but BC doesn't come out then your timing is good. if you mess it up and summon the assist just reset from the menu and repeat.
you can vary how far you fly by holding the step direction when doing the input. if you don't hold the step you won't go as far but a lot of the time that's ideal. once you can do this successfully at any time without having to think about it then you're ready to start learning the rest of the suit.
General Strategy
1. movement.
this is the reason i play the suit and it's his most powerful asset. his turning, speed, amekyan (melee/2b ->csa), achakyan, turnaround shot (turnaround A ->BC with assist out), etc are all superb. the key to beating stronger suits is to outmaneuver them combined with bombardment. experiment with his various fast falls and try swerving around projectiles instead of hard dodging
2. funnels
just throw funnels any time you aren't actively attacking or defending. throw them when approaching, when running, throw them at people who aren't looking, etc. throw one or two at a time then pay attention and see if it's possible for the funnel you threw to hit then be ready with a gerobi or at least a zunda. the funnels have a unique stagger effect to give you more time for punishing and they reload quickly so don't worry about wasting them.
3. shotgun (CSa)
I would tell you how to use this but it's a really weird weapon and I can't explain exactly how to hit people with it. The only way to really hit people is to use it on angle at a specific range. It works in situations where a BR doesn't but it also fails in equally as many situations where a BR would work due to its delayed firing and lack of tracking. I recommend using it all the time even if you aren't hitting people, it's the only way to understand it. You should also be charging A while firing your BR so that CSa is ready when you need the achakyan. if you don't need the achakyan or think they're gonna land just fire it and boost forward to follow up.
using the achakyan will also give you a new way to hit people as you can move in ways they won't expect while the CSA comes out. doing 6b forward rainbow step BC->CSa is a good way to put on sudden pressure and grab otherwise unpunishable landings.
occasionally you can wake up from a knockdown and use CSa's close range tracking to blow an aggressive melee suit's head off. I don't recommend doing it too often as the opponent can easily read and punish it. This is a bad habit of mine as I bet on the muzzle correction to get me out of a jam but instead end up in a worse position when it fails.
4. gerobi
if achakyan and movement are 50% of sazabi's power then gerobi is the other 50%. BR's and funnels are nice but they don't hurt very much. in fact almost nothing sazabi does hurts very much compared to all the other 3k's. this is where gerobi comes in, it's crucial to hit people with gerobi so that you can get some damage on the board. the tracking sucks but the startup and speed and width of the beam are excellent. you should always be looking for an opportunity to land gerobi because if you aren't then you will most likely fall behind in the damage race.
try using your BR's and funnels to make opponents move then sneak in a landing with a fastfall when they are in the air. once you have the ground and they are in the air spending their boost you can begin planning to line yourself up and get the right height for a gerobi punish on their landing. keep in mind that the opponents will be looking for this as they know it's your only damage dealing weapon, so expect them to boost out of the way or try something else just before the gerobi would hit. get familiar with how fast it is and how poor the muzzle correction is so you know not to waste time firing shots that won't hit. at the same time don't be afraid to throw it out if you aren't being shot at because the reload time is very good for a big weapon.
5. melee
sazabi's melee is pretty shitty for a 3K. in terms of winning exchanges it isn't horrible, but the tracking and distance he moves leaves a lot to be desired. the damage is also mediocre, his best combo being cc8b 1hit > bbb > BR for 241 damage, less if finished with CSa instead of BR. occasionally you can bait people into a melee fight then achakyan in their face or something but I wouldn't recommend it against serious melee suits like Master or quanta.
Well I didn't intend to write this much but here it is. Remember that in general there's always something you can be shooting or throwing at someone with sazabi. firing shotgun, throwing funnels, threatening with gerobi, etc. he's a barrage type fighter who forces his opponents to spend boost while landing in between enemy shots. rely on having the boost advantage to win fights. anyway that's what i try to do, good luck.