Tarmac is generally considered to be the cheapest method of laying a hard surface. But it's a time-consuming job which requires specialist tools, machinery and, not least, knowledge. This means that it only becomes the cheapest method once the driveway is up to a suitable size, where the economies of scale kick in.
For these reasons, tarmac is not something that can reasonably be considered as a DIY job, unless you have friends or relatives in the trade who are going to help you out, particularly with the machinery.
It's not really a good surface for a recreational patio or other garden area, as it's not that attractive and can get hot in summer, which is when you want to use that space. Having said that, you might want to have an area in the garden for kids to play ball sports or games on, if you have the space. If you're going to get a drive laid anyway, the extra cost of doing part of the garden won't be a great deal more, since the people, machinery and supplies will be coming to you