Alright I will give a few suggestions for your army that I would do if I were you.
The Commander I would reconsider the shield
gen just because it cost a lot. I would replace it with drone controller and give him 2 marker drones instead of the shield generator.
Also the cyclic ion blaster is a cool gun but I would just give him another plasma so would be
Commander with:
plasma
plasma
drone controller
stim injector
target lock
2 marker drones
You are missing markerlights as a whole you have NONE and you need them
For the XV8s I would give them all target locks, all marker drones and either two plasmas (not twin linked) or two missile pods.
Firewarriors I wouldn't take the Shas'ui or bonding knife and I would bring another unit of them or a unit of Kroot (possibly with a hound) but defiantly with sniper rounds.
For hammerhead I wouldn't take the decoy launcher or the auto repair system I would take disruption pod and then take longstrike makes it a lot better. The submunition rounds are nice though.
SO just a few loadout changes and add markerlights from drones attached to the XV8s.
As for expanding your army your best bets would be to get 2 broadsides, some kroot for more troops (because your firewarriors will probably die fairly quickly) and some pathfinders for some markerlight support.
SInce you do have 3 stealth suits I would bring them with the burst cannons because at 90 points you have a slot for them in the elite section. Just deep strike them in behind enemy lines where there is a squishy unit and then just blast them with 12 burst cannon shots.
Same with the piranhas I like the ones I have I find them useful because just at base points value you get 2 gun drones attached which is awesome. Basically 2 gun drones cost 24 points so essentially you are paying 16 points for a 2hp skimmer with a burst cannon. Again I just deep strike mine attack something not to hard to kill and detach drones.
Those 2 units will just help you distract the enemy as you fire at more dangerous units.
Just a few suggestions, everyone plays differently and I am not a power gamer so lots of people might disagree with some of the stuff I said
Automatically Appended Next Post: So I didn't actually show you what it would look like but here is what you COULD do based on what I suggested
This will give you markerlight support that you need and bring you up to 1250, not the best list but still will do alright.
This would just involve buying a group of kroot and thats all to get to 1250. If you replace the piranhas (probably the first thing to replace) and stealth team with broadsides and pathfinders that would be best tho but this is based on the least amount of money spent to get where you want....budget gaming

Hopefully my math is right on this one.
HQ
Commander
Drone Controller
Target Lock
Plasma
Plasma
2 Marker Drones
152 points
Troops
10 Firewarriors 90
10 Firewarriors 90
13 Kroot sniper rounds 91
Elites
3 XV8s each with
2 missile pods
Target lock
2 marker drones
243 Points
XV104 Riptide
Ion Accelerator
TL SMS
Early Warning Override
190 points
Stealth team (stock)
90 Points
Fast Attack
3 Piranhas (stock)
120 Points
Heavy Support
Hammerhead
Longstrike
TL SMS Drones
Disruption pod
185 points
Total points 1251