Springs and dampers before ARBs for sure, be they coilovers or individual units.
If it's still rolling too much, for mixed road/track use ARBs are a better option, as long as you go bigger at the rear than the front, to make the rear more mobile.
Go too big on the front ARB, or too stiff on the spring rates, or both...and it'll understeer in the wet.
Too stiff on either and it will be reluctant to turn in as well. It's all a balancing act.
Set the front suspension up quite aggressively to find some more front end grip and you will be on the right track, preferably with an LSD and sticky tyres...
Poly rear beam bushes make the rear more predictable.
Personally, for a 16v on Koni coilovers, I find the front springs too stiff for the car (with Eibach ARBs) and want to soften the front springs slightly to aid turn in...I could drop to the standard front ARB, but I like the balance at the moment...it's just too crashy over bumps...so I would see dropping to softer springs and keeping the front Eibach ARB is my solution, for my car.
It's perfectly acceptable to go harder on the springs and ditch the front ARB all together though...it'll just make the car awful on the road.
As for the rear beam...there is little you can do to make a difference unless you are running slicks/R888s and generating some serious cornering forces, in which case a braced beam may help stop camber/toe changes as you corner, at the expense of unsprung weight...adding negative camber at the rear will also help in that case...but both only work if you have LOTS of physical grip at the front - most Mk3s don't.
Bottom line is; there is no one size fits all answer.
you need to understand what it's doing, and more to the point, not doing, then address the problems.
Just saying do this, do that, doesn't work, as every car behaves slightly differently...and more to the point, every driver likes the car set up differently.
I have a mate with a Mk3 VR6 track car that's really well sorted and quick...but it understeers due to that boat anchor at the front. He doesn't find it does...as he drives round it to some degree...then uses the extra power on the straights.
I prefer to trail brake and really load the front end up...so need as much grip as I can find, to carry corner speed.
His suspension set up is quite different to mine, despite sharing the same coilovers/ARB set up....
Which brings the set-up back into it:
You can fit the best suspension on the planet, but if you don't have decent tyres and the suspension set to work them properly, you are not getting the best from them.
