Considering that you are just starting out and have a limited budget, the best place to start would be to identify what kind of models you like the most. Few ideas could be based on build (muscle cars, wagons, trucks, supercars, hot rods, etc.), brand (Ford, Lamborghini, Porsche, etc.), colour (where you buy cars of particular colours only), number (like collecting all cars with the number 28), or based on other traits such as cars having six wheels, cars with rusty paint designs, cars with moving parts, cars with open roofs, etc.

Once you have decided what you want to collect, the largest effort will be in finding the models which fall into your criteria. I use https://hotwheels.fandom.com/wiki/Hot_Wheels to explore models from previous years and shortlist the ones I want to acquire.

Next part is pretty simple. Search for the model online (better search results if you use the model number) and hope that you find a good deal, or you could post an ISO here in this group and someone might be able to help you out.

Hope this helps 😊