I think few people, especially starting out, will need more than a Vamo v5 (or an iTaste MVP), a few batteries and a Nautilus Mini with a couple of packs of heads. Bang on kit for not much outlay.
Only problem with the Vamo is how damn easy it is to knock the thing over.
While this is true, the question that was asked was for a decent budget. A decent budget takes you into a different league with respect to the vape quality, so long as you buy correctly.
More over, decent kit commands a premium second hand. Second hand vape gear is just about the only gear I have come across that regularly sells for anything up to 100% of the purchase price. 80% being VERY normal. So even if you fork out for top end gear, if you find it isn't for you, it's relatively easy to sell it on at not much of a loss. Certainly less of a loss than if you were to buy one of the usual "starter kits" at £40 which are worthless once you are finished.
Example being that KFL+'s often sell for only a tenner less than rrp, and a DNA30 mod from one of the mod builders will often sell for only £20-£30 less. So, if you have the budget to begin with, you can essentially try out top end gear, without losing any more money than if you bought a starter kit. If you like it, then you have already got top end gear, without having to write of the cost of the starter kit.
Granted though, you would only lose a tenner (maybe £15) on an MVP probably. And you could probably sell an aerotank or similar for a tenner, so it might be a slightly smaller loss, but if you did like it, you may feel you should have forked out properly to begin with.