Sometimes I think the game is way too hard without a bit of abuse. Whether hire/fire cost avoidance, smoke grenade spam, or in my case, restarting the mission when losing a soldier.
Anyway. I disagree about keeping all UFOs for disassembly. Your workshops will run pretty much 24/7 anyway, and it's better to sell the shot down UFOs right away, instead of having to build extra workshops and UFO yards to keep up with the flood of UFOs. Besides, selling UFOs right away to some nation adds to its happiness, and more happiness means more funding. You can even sort the nations by happiness in UFO sell window. Just keep the landed ones and first of new type for research.
About bases...I run four. Main base near coast of southwest Anatolia, this covers (with advanced radar) whole Europe, part of India and most of Africa. Second is pure workshop next to it that also provides some SAM defenses, no radar there. Third is in North America (would have to look but I think I build it somewhere in Florida). Fourth is...Borneo or somewhere there, that covers area from India to Australia and south Asia. With radar bases at Siberia, South Africa and Argentina, I've got most of populated areas covered at reasonable expenses.
Money management is big part of the game. You have to think really hard about what you need. Workshops are useless except in dedicated workshop bases IMO because production is too slow. Similar for laboratories, although it's possible to build effective 2x interceptor/1x dropship/radar/research/SAM base, your main base should definitely follow that layout. Once you build advanced radar in a base, take down now useless radar facility so you don't pay for its upkeep. Don't stockpile ammo too much in advance...especially craft ammo is expensive and unless you are running out, not worth buying more as you'll be phasing it out anyway. Alien artifacts pay a lot, so think about those. Kerrblades, alien armors, plasma blasters are all useless once you research them. You'll be capturing far more plasma pistols, grenades, blades, rifles and rifle ammo than you'll ever need, you'll be phasing plasma rifles out eventually for EP assault rifles. And so on....