You must have a Philips Hue Bridge to enjoy the full benefits of the Philips Hue lights. And given the prices today, you're best going for the latest version, the Philips Hue Bridge 2.0 which is the only one readily available, plus it's cheaper than the prices for the older model.
Don't worry, you should only ever need one bridge, as it can handle up to 50 connected lights, so unless you're planning on out-shining Vegas anytime soon, you should be fine.
The Philips Hue Bridge is the brain that connects your bulbs to your home internet, allowing you to control them via apps or Smart devices like the Echo Dot or Google Home. So if you want to change the colours and shades of your ambiance bulbs (and why else would you want them?), make sure you've got one of these, either from the standalone prices below, or included in one of the many Philips Hue Starter Kits available, the later are arguably better value as they come with bulbs too.
If you already have some bulbs and just want the Philips Hue Bridge brain box to run them, then you'll find the best deals below. One last thing though, the Hue Bridge requires a wired internet connection to your router, so make sure you have access to it before diving into the world of Philips Hue lighting.
Or get one with two bulbs for £10/$10 extra
If you don't have any bulbs yet, this is the cheapest Philips Hue Starter Kit and includes the Hue Bridge 2.0 and a pair of regular-sized white screw-in bulbs. You might also know them as E27 bulbs in the UK, or A19 / Edison bulbs in the US.
These are the most basic Philips Hue bulbs and don't change colour or 'temperatures' of white but still include smart features like dimmer lighting, timers and remote switching (via smart devices). So if you fancy having a few very basic smart bulbs in addition to the mad colours you're putting in other rooms, this is a cheap way to grab a couple.