End-to-End and back again
There are also cloud services that have been created by some manufacturers of popular embedded devices. With these, you get guaranteed-working hardware with wireless certifications all done and ready to go. They provide the data storage and event messaging services and APIs that you would expect from other cloud IoT services, and you can also expect a high level of integration between their supported hardware, APIs, device libraries, and documentation. In particular, one headache that is taken care of for you is secure and reliable product provisioning and firmware deployment. These two things are very hard to DIY right, so it's best to leave it to the experts.
Two examples are Electric Imp, who create a number of "impModule" IoT-focused plug-in boards, and Particle.io, makers of the popular Photon, Electron and Particle Mesh microcontroller boards. These services could provide an easy ramp up if you're already a fan of their hardware. They both provide small-scale quantities for hobbyists with the hope that your success will lead to enterprise-level hardware purchases.
Particle.io focuses on supporting a prototype to rapid production business need. In addition to supporting their WiFi-only Photon, Cellular-only Electron and next-gen Mesh (which has BLE and WiFi or Cellular), they also have first class support for running the Particle firmware on Raspberry Pi. The API provides webhooks, and a REST interface, and socket-based publish/subscribe messaging interface. Finally, Particle also provides a desktop and web-based IDE for working with their devices, libraries, and cloud APIs.