Head on a brigalow homebrew

Most kits include a can of "malt extract" and some yeast to which one adds some sugar and a lot of water before fermenting it. IMHO the best (and perhaps most natural) way to improve "head" and "body" of a kit beer is to add more pale malt extract instead of sugar. An equal measure of liquid malt extract or a little less dry extract will do. The measurement does not need to be very precise. Doing that will "thicken" the beer by adding a small amount protein and a lot of polysaccharides that will, amongst other things, improve the structural quality of the foam and aid head retention. One can increase the head developing potential by using wheat malt extract not just barley malt extract. (The next step would be to buy and use pure malt extract and add your own choice of hops). IMHO the main reason many "economic" beer kits don't foam well is because there is not much on them.

Carbonation can be achieved in several ways and some are more reproducible that others. The simplest way is to add a known amount of sugar to the brew after fermentation has finished and then bottle/keg it. I prefer adding this to the beer by transferring the beer from the brew bucket onto a solution of the sugar in a clean bucket. That takes the beer off the dropped trub/yeast in the brew bucket and allows me to uniformly mix in the sugar without making the beer cloudy. I find 120g of sugar per 24 litres of beer gives a mild carbonation and 150g sugar(or dextrose) per 24l gives a good gassy carbonation. Other prefer to add measured amounts of sugar to each bottle. 3g of sugar/glucose per 500ml bottle will give a reasonable carbonation. Friends have used one heaped teaspoon of sugar (via a funnel) for each 500ml bottle. IIRC carbonation drops are usually designed/dosed for 330ml bottles and the recommendation is to use 2 for 500ml bottles.If you have carbonation drops they are convenient to use but IMHO they are not worth buying as one can use sugar to carbonate as easily and more cheaply.

If the beer seems well carbonated, it is possible that the problem could be with your glassware. Some detergents, particularly dishwasher rinse agents or those with drying agents can put a film on your glass that can cause poor head retention, but if you're not having the issue with other beers (commercially bought, for example), then this may not be the cause of your problem.

An alternative could be the type of malt used in the recipe. I believe, though would struggle to elaborate being new to the homebrew scene myself too, that the proteins in the malt can aid head retention of the final beer and some malts offer more of this type of protein. It could be the kit that you used may have been closer to the end of its shelf life or that the proteins which aid head retention in the particular malt used by the producer are not as prominent as in other malts.