If we talk about research and discoveries in the XCOM 2, there are more than enough options. New game includes a number of powerful ways to develop at an early stage of the campaign, so that the decision about where to go you will have to take very soon.
Determining what and when can explore the impact on structures, training, weapons and equipment, to which your soldiers will be able to access, impacts on future progress, mission planning and style of play.
Way presented in this guide is focused on the research, which can be run at the beginning of the game, opening a lot of upgrades.
Basic research: Biotechnics aliens> Psionics
Secondary benefits / Discovery: Alien Autopsy> Advanced Combat Center> Mental Shield> Advanced Psi Power
Those who want to get access to the class of Psi-Operative, should follow this path, so that will be able to discover the unique capabilities of its soldiers, applicable both in defense and attack.
Basic research: Biotechnics aliens> Modular Weapon> Opening ADVENT officer> Hybrid Materials
Secondary benefits / Discovery: Alien Autopsy> Advanced Combat Center> Magnetic Weapon> Polygon> Plate armor
If you do not pursue a psionic, you can spend time and resources on pumping standard soldiers. The only problem is that it is expensive and time consuming.
Advanced Center allows you to quickly loot soldiers. School guerrilla training could be built in the beginning of the game, opening the soldiers such things as lightning strikes, increasing mobility on the first two turns of the mission. Wet matter provides a 25% Bonus. Squad size increases the amount available in the detachment of soldiers from 4 to 5.
Way of Weapons and Armor
Basic research: Modular Weapon> Hybrid Materials> Magnetic Weapons> Plate armor
Secondary benefits/Discovery: Magnetic Weapons> Research Gauss weapons> Armor Predator> Arachnidian suit> E.X.O. suit> Alien Autopsy
This expensive way ignores the advantages of individual training or creating things in the short term, for the sake of long-term buns in the form of better weapons and armor for your soldiers.
Modular tool, not only allows you to modify an existing weapon parts that you find on the tasks, but also causes the most damage aliens through access to Magnetic weapons.
These are just three options of how you can develop in the early stages. You can choose own way, by combining individual elements, though in this case achieving results will require more time.