I find Vallejo Model Air paints to be very easy to use & they have a wide range of colours. The Model Air paints apparently have finer pigments than the Model Color range & are designed to be airbrushed straight from the bottle, though I habitually add an M5 stainless steel nut "shaker" to a new bottle + top it off with the Vallejo thinner before I start..
Also had good results with Lifecolor & Tamiya acrylics, but would not recommend Humbrol – coarse pigments & I found that they became too diluted to cover when thinned enough to spray without clogging. Using Vallejo Thinner Medium (in conjunction with Humbrol thinner) helped a bit, but unless the particular colour is only available from Humbrol I give them a miss now. That said, I think Humbrol are re-formulating their acrylcis & moving to dropper bottles from their current tubs, so things may cahnge there. Tamiya acrylics are very forgiving, but require the use of their thinner for best results.
The Vallejo & Lifecolor (and from what I can gather AK and Mig Ammo) need to be applied very sparingly and the colour built up with multiple thin passes – the paint should never appear wet on the surface. It took me a long time to twig this, but once I knew how to use them they give excellent results. It is as though the surface changes colour with no noticable paint thickness & they are very economical to use.
The Spanish water based acrylics don't adhere well to unprepared surfaces, though, and a suitable primer is recommended. I use Vallejo's polyurethane primer on plastic models – this is applied differently to the acrylic paints, being applied quite heavily & keeping a wet edge. It also takes a couple of days to harden off sufficiently to sand cleanly, but dries to a very thin satin finish layer that does not obscure detail.
Vallejo (and Mig IIRC) have some "how to" videos on YouTube (if you can stomach YouTube's increasingly obtrusive adverts) that I found very helpful. The plastic dropper bottles are easy to use & the paint has very little odour. Mrs B complains about Tamiya acrylic, which has a slightly alcholic smell, but not Vallejo or Lifecolor.
I don't know where you are in the country, but in Yorkshire there is a department store chain called Boyes that has the Vallejo paints, primers, thinners & airbrush cleaner on the shelves.
Best getting a couple of bottles to try before you dive in – you can "invest" a suprising amount before you know it.
HTH
Nigel B.