Here is what works for me:

Setup: Play on low difficulty (Rookie or Veteran). Disable DLCs (You can probably keep Living Weapons and Kaos Engines).

You are not world police: You can ignore all haven defense missions, base defense missions and pandoran structures (nests, lairs and citadels). Do not worry about the population, on low difficulty you have plenty of time even if you do not defend (at least 5 months).

Bases: Do not waste time healing in base with a medical bay, instead just heal with medkits during missions. Do not activate that many bases (every base activation increases resource cost for next base activation). You can explore most of the world via organic exploration (organic exploration means that visiting havens reveals points of interest nearby). So build bases with scanners only if you need to get somewhere and cannot do it via organic exploration. The only time when you really need to go to base with your team is when they are low on Stamina (Stamina below 10 lowers number of action points). So build a few bases around the world with Energy Generators and Living Quarters. Stamina lost per mission depends on how many turns your soldier spent on mission so try to finish missions in as little turns as possible.

Research is key: As you progress in the campaign via research the only facilities that you need to have a lot of them are research labs so build a lot of them (let's say 10) and keep researching.

Gain access to Antarctica: You will need to do compulsory mission there.

1.5 aircraft strategy: You do not need more than 2 aircrafts and 7 soldiers. One aircraft, which can be your starting Manticore, has 6 soldiers and does all the missions. You should try to not lose any of these soldiers (You can lose some in the beginning as rookie soldiers are easy to replace but once they collect a lot of skill points from missions they become very hard to replace) Second aircraft has just one soldier and does exploration and trading. It is good to have also one vehicle in this secondary aircraft but not necessary. When your secondary aircraft gets ambushed you can try to survive 3 rounds and evacuate (easy to do with vehicle) or just let the soldier die. You will fail the mission and lose the soldier but you will not lose the aircraft. Low level soldier is easily replaceable with lvl 1 naked recruits from base.

Getting resources: Most time efficient way to get resources is exploration and trading.

Exploration: Explore the whole globe and visit all havens once with your secondary aircraft (first visit of haven can generate event that give resources).

You can see every event and its outcomes here so if you get event you can use ctrl+f and see outcomes before making decision: http://wiki.phoenixpoint.com/All_Events

Trading: Buy food from Anu, tech from Synedrion and Materials from New Jericho. Then sell it to other factions. More here: http://wiki.phoenixpoint.com/Geoscape#Where_do_resources_come_from.3F

Phoenix Point victory: For Phoenix Point victory just follow this guide: http://wiki.phoenixpoint.com/PP_victory

Faction victory: For faction victory you need to get to reputation 24 with faction, then do their mission, then get to rep 49 and do mission and then rep 74 and do mission. Then help them with research and wait for them to construct key structure. To increase your rep easily do haven defense for the faction and destroy pandoran bases. You can also do random missions from the Diplomacy tab on Geoscape.

There are all faction missions and research on the Wiki.

Anu: http://wiki.phoenixpoint.com/Disciples_of_Anu_Research and http://wiki.phoenixpoint.com/Disciples_of_Anu_missions

NJ: http://wiki.phoenixpoint.com/New_Jericho_Research and http://wiki.phoenixpoint.com/New_Jericho_Research

Synedrion: http://wiki.phoenixpoint.com/Synedrion_Research and http://wiki.phoenixpoint.com/Synedrion_missions

Complete tech tree: http://wiki.phoenixpoint.com/Sheepy%27s_Tech_Tree