I find an 18volt combi ideal compromise between power and weight.
But try handling a few, remembering that the battery is most of the weight, and big batteries are popular. Perhaps you don't have big muscular wrists. 12v is adequate for light work only.
Anyway, get two batteries so you can charge one while you are working.
Brushless motors are said to be more efficient, but the speed changes in steps rather than seamlessly increasing as you push the trigger more, and they are more expensive.
Your budget is high enough that you don't need to get an own-brand from a DIY shed or discount supermarket, but I think not high enough for a Makita or Milwaukee. If you are a DIYer you will do as much work in a year as a builder does in a week, so you don't need the same durability. Say, an Ebauer or a DeWalt.
When buying tools, get them shortly before you start a major project, so if it goes wrong you can take it back for refund or exchange.
A plastic case with a set of drills inside is a useful accessory and usually included.
You can buy a big kit of drills, but you will end up only using about 4 of them. A set of a dozen HSS and four Masonry will do you. Screwdriver bits are very cheap in sets, made of a special hard steel, and wear out quite quickly. You will need Pozi and Slot. Phillps are seldom used unless you are in America or have a 1960's car. If you see a big kit from a reputable maker buy it and one day you may have a use for one of the others.
If you have any heavy work to do, drilling concrete or hard bricks, or chiselling out chases or removing tiles, you will need an SDS+ and set of bits and steels. It will be too heavy to use for anything else, and get a mains powered one unless you are a millionaire.