One of the first wireless lavalier systems I ever used was the Sennheiser G3. These kits are everywhere in the independent and documentary filmmaking world. And there's good reason for that: They're solid and reliable. Yes, you'll need to read the manual and learn how to use them and set up them up, but once you've got that down, they work reliably, are well built, and have some nice features like locking 3.5mm plugs.
These transmit an analogue signal. This is what most of the pro-level wireless systems do and there are some advantages to that. First, you're not sharing the rather overwhelmed 1.4GHz band with all the WiFi, Bluetooth, and other consumer electronics enabled devices out there (mobile, cordless phones, etc). Also, there are potentially distance benefits as well. But of course, you do need to buy a device with the right frequency band for your region so if you do look seriously at these, you'll want to research which band is suited for your region of the world. For those in the US, B&H is recommending models which transmit in frequencies below 600MHz. And the FCC has some FAQs here.
B&H has several kits at the regular price but with some bundled items which make for a good deal: a $100 B&H gift certificate and a case similar to a Pelican for the kit. I'm told that these bundle deals last through the end of September.
There's a dizzying array of model numbers, but here's the basic G3 kit with the ME2 lavalier microphone and a coldshoe mount receiver.
And here's the same G3 kit with the ME2 lavalier but which also includes an XLR plugon transmitter for handheld mics.