With 3 hangars in my main base (southern Europe) I am usually able to reach most missions and have my cars/vans return, before more missions pop up. Still, I prefer the flexibility of having shorter travel distances i.e. several bases across the globe. Besides, I will need more space eventually and since it takes quite a while to build up bases, especially if you want to make them as defensible as possible, it is better to start sooner rather than later.
So I start my second base almost immediately. Both East Asia and North America are valuable areas to protect. I usually go for NA for my second base, because it is slightly farther away from my first.
It is possible to run out of money, before it becomes operational (hangar, living quarters, gym, storage, prison, animal pen). I also prefer to build an intelligence center and bio lab in here, rather than in my main base (or in both, if budget permits).
I aim to have 3 bases up and running by the time, that helicopters become available. That way I have almost global reach with helicopters and later with Dragonflies. Also, with these three bases in the locations I mentioned, you will be able to reach every cult HQ with an Osprey (I buy only one and transfer it around bases as needed).
In the end I want to have 5 bases, like in vanilla, to get global radar coverage (yes, AWACS exist, but I'm sure I'll need the space eventually, anyway). I hope to have them fully decked out with radar, interceptors, troops and whatever else I need before 1999.