Well, these kind of questions are very vague, and there's no real right answer onto coming up with a perfect team. But, there are some ways to consider maybe what kind of Pokemon will go hand in hand with each other.
1) You don't really want a team with all of the same-typing; want to be sort of equally balanced throughout
2) Consider having a mix of attackers and defenders
3) Some popular strategies:
- Moves that work with Moves (Fusion Bolt/Fusion Flare)
- Moves that work with abilities (Sunny Day/Chlorophyll)
- Abilities that work with moves (Hail/Blizzard)
- Abilities that work with Abilities (Drizzle/Swift Swim)
These are just some of the few standards you want when making a team, and this a good start into knowing what Pokemon "synergise" with one another. However, if your still stuck, this website provides very helpful information into considering moves slots, stat distributions, and even good team options for any Pokemon of interest.
Hope I helped! :)