^My advice: be aggressive with the base management and cautious on the battlefield. The most important thing is to get off to a solid start and get as much cash as possible. Focus on getting as many satellites built as you can afford, with South America & Africa being the priorities since their bonuses give you instant autopsies/interrogations and an overall cash boost respectively.
Also capture as many enemies as you can early on because those light plasma rifles will come in handy later. even more so if you follow my advice and skip right past most of the laser weapons and go right to plasma asap. You'll still need laser rifles and pistols, but I wouldn't bother with the scatter, sniper or heavy.
As for the armour, all you really can do is settle for carapace armour until you can get to the titan armour. Don't worry too much about the more specialised ones until later. Oh and nano vests are literally a lifesaver early on. All assaults not carrying the arc thrower should be so equipped. Grenades just aren't worth it till *much* later.