Intel Pickups are the primary method of acquiring Intel Points. They can be found in enemy NPC bases and, upon interaction, grant the user Intel Points, that can be later spent to discover Tech Tree Entries. 

Intel from level ups stops around level 125 or so. Further exploration and engaging in encounters with stronger NPCs will yield more Intel Points per Intel Pickup, allowing the player to expand their knowledge and gain access to new items/equipment/weapons/vehicles.  

However, there's an overall intel cap which is the total amount required to buy everything.