Hey and welcome to TC,
The good news is, we have all been where you are now, we all had to start somewhere and I also had a lowly carb fed 1.2 Nova at the beginning. I would suggest leaving the engine in place and not really touching it for the time being, I'm assuming this is your first car (correct me if I'm wrong) so doing anything engine wise will kill you on the insurance as will most mods. If you plan on keeping the car for a long time then I would sort the brakes, suspension and stiffen up the chassis ready for an engine swap when you can allow for one, the 2.0ltr 'redtop' XE is a popular conversion into Corsas and Novas and they sound amazing on throttle bodies. If instead you want a quicker car that isn't a Vauxhall, leave it as it is and save your hard earned for something you really want and is quick enough in standard trim in the future.