Never too old! There is a guy up our allotment who is 96! There is another who is partially blind too!
The spikey flower head is actually an allium, it was on it's way out when that photo was taken but if you google alliums pretty much everything that will come up will look more akin to what it is in bloom π They are quite pretty and certainly grab some attention.
Veg tends to be either given to us or we keep things back from last year, i.e. all our potato's that we grow next year will be whatever we have left over this year just put in the ground π
As for flowers, the dahlia's are my go to and you tend to pick them up as tubers or small plants. Again if they grow well and I'm particularly fond when the tuber's get over a certain size you break them up when you store them away for next year and essentially you get multiple plants of the same sort.
If I was to buy seeds it often varies, I have had success with a couple of stores on ebay, suttons is quite good as well or dt browns π But otherwise most of my stuff tends to come from a little garden centre I found a few years back that I'm quite fond of.
Aggh don't test me π Nothing of mine ever looks pretty (unless I just take a cutting of a single flower head π ) Gardening is a patience thing most definately, it's why people tend to just buy flowers each year and throw them in their flower beds but at home we have tried to build up a garden using plants and flowers that come back again each year. We have a couple of camellia's which are lovely (flowering season is a bit short though). The other things is the type of soil you mentioned earlier, like certain flowers don't like acidic or alkiline soils, at home we have clay soil which is horrible to work with as it means your plants sit in water when you get crap weather and it dries out in the summer so you need to consider that (or as we are, you spend time each year working in compost and the such to improve it).
Gardenings just a vast subject π I have considered doing a course a couple of times, it would be one of those things that if I could pick any career and money wasn't an issue I would likely be a gardner I think.