It makes more sense to treat Crimea and Donbass separately. Putin undeniably gave the orders to occupy and annex Crimea, but that did not immediately trigger armed conflict in Donbass. The latter really started when Strelkov and his band occupied Slavyansk, and based on the information that we have so far, it appears to have been a private enterprise that wasn't sanctioned from the Russian government.

It took them a while to decide whether they want to back it or not, evidence to which can be found in many photos from the region from 2014 - if you look at early photos, the separatists carry a very wide assortment of arms, many of which are clearly civilian in origin (SKS and even Mosin rifles, for example), and only a few had AKs - and even those were stolen from Ukrainian army depots and such, and have the telltale early model wireframe stocks. Whereas from August of 2014 on, you start seeing most armed with standard Russian issue AK-74M (with solid folding stocks), and quite a few decked out in full sets of Russian "digital Flora" camo complete with helmets, load bearing vests, and body armor. Also, a lot more artillery and armor.

Coincidentally, that was also when Ukrainian Army and National Guard advance was stopped, and the first major setbacks (e.g. Ilovaysk) occurred.