Buy your stuff from a home brew shop. The shop will tell you a whole heap of things about brewing more than just buying a kit at Kmart or whatever. The problem is most people who buy the kits give up after a couple of times. Buying stuff from a brew shops gives you more confidence and you have backup and advise if things don't go right.
Don't use just dextrose as a brewing sugar. Use liquid or powder malts instead. Buy in bulk and get a set of 5KG scales to weigh your 1 Kg brewing sugar. Like buy say 10 kilos of malt at a time instead of buying individual packs. It's cheaper. Make sure everything is sterilised and clean. Don't add boiling water into the fermenter with powedered malt. It will go clumpy. Add corn syrup to give better, fuller head
Get a bench capper. Hand cappers are ****. Keep bottles in a dark, cool place for minimum 3 months and up to 1-2 years. Experiment when making stouts. Add some extra hops, maybe some chocolate grain or black barley to give it more 'kick'.
As I said above, go to a brew shop and buy your kit! You don't need a pretty cardboard box with Coopers name on the box.
The brew shops have many different beer kits (meaning the cans). Buy from the supermarket as the Coopers kits because it might be 2-3 dollars cheaper. Experiment and don't give up. Keep going and it can only get better.