Use the recruitment viewer to see which provinces give you the best local troops (both quality and quantity, depending on what your gameplay requires). I usually develop 1 province militarily for every 6 or so. This provides the local defence force and cleans up rebels for the others, which can then focus on building the economy.

I try to keep sections of the map more or less autonomous, so that I can use my factional armies where I need them guarding and expanding my borders. Once pacified, areas like Iberia, Gaul, Britain, North Africa can all look after themselves, with minimal investment in building MICs.

Other than this single recruiting centre (Gov 4) I use the highest available government, so that I have the widest range of economic building to develop.