bin the power steering and all the heavy items that come with it, and sap engine power
and what Ian says,
and thats about all the weight you can shed without getting into big expense of lightweight/custom panels i should think.
as for brakes, there is a couple of large discussions on here already from some time ago where a lot of folk pout uo there big brake combo, have a search for 33 brake upgrade and i'm sure you'll find it, but losely you'll find people have used items such as the Alfa 75 master cylinder which is bigger than the 33's, and then a combination of calipers and discs from anything from Fiats, daewoos, and i think Johnboy found a set of calipers from a calibra v6 are a pretty straight forward fit if i recall correctly, but its all in the thread anyway, but remember your wheel size is one of the biggest limiting factors.
as for handling stuff, as mentioned already, stiffen the chassis with strut braces etc, anti roll bars are beneficial, but i'd personally address the need for those lastly, as they will be mostly bespoke/customised part at best, and i would rather sit the car down on the suspension mods first, and then see where you go from there.
commonly fitted, including my own 33, are the Koni struts and H&R springs, and are a good combination for the budget conscious, but mine is a modified road car, so for more track use i would aim for lower that the H&R springs will go to.
you probably want to start thinking about getting to sit down something like 2-3" lower than stock to get the centre of gravity down, and the stiffness you're going to need, whereas the H&R springs i have are only about a 35/40mm drop, but i have a little extra stiffness from 17" wheels with 40 profiles, so that i can get bigger brakes in that the lads only using 15's! ha ha!
i think the koni's will cope, and if you can stretch to the extra money, get the versions that are multi adjustable and on the car, rather than those that you have to strip to adjust and are only adjustable for rebound damping only, not compression damping, but they all work well to be fair, so maybe a set of those and some custom springs would be a good starting point to get you stiff and low!
thats my advice for starter mate, and good luck with it all, it'll be great to have another 33 out there in competition!
all the best