Going to Aus was on my own – I was 17 ( 1978- gulp) I had a job organised to start with tho on a farm.
Round the baltic was done by myself as well – except at that time (1990) you could only enter the USSR on a motorcycle as part of an organised group so I joined up with one for the USSR leg.
South America I went to with operation Raleigh as a medic and carried on travelling for a couple of months afterwards.
I would start in somewhere not too unfamiliar such as the antipodes or south america. Its very dislocating and confusing going travelling so minimising culture shock early on can help. Then as you get used to things it becomes easier to go to places that are more different such as India or laos
I think if I did this again it would be cheap bikes – so that they could be discarded if they became a pain and public transport for longer distances.
Having your own vehicle increases cost hugely and also ties you down unless you can discard the vehicle if things go wrong.