Basically, what would your Pokémon team be if you had to factor in budgets from what it takes to take care of them? Here are the rules:
No Legendaries.
Certain types will be easier to take care of than others, and giant fully grown Pokémon will be very difficult to take care of on top of their type. You have a budget of 8,000, ignoring any increases in the near future. Because I can't possibly account for every Pokémon there is, there might be a few loopholes:
>Grass, Water, Bug types, any Pokemon that generate their own energy from natural processes = 300
Most Grass types are docile and can use photosynthesis
I imagine Waters can thrive on minimal food but require a lot of water

>Normal, Psychic, Fairy, Flying, Fighting, Ghost, Steel, Rock = 500
These types probably need a bit more love and care than other types, but are unlikely to cause any issues aside from that. I imagine Ghosts need a specific kind of energy to be taken care of, so I won't be boring and say 0 for them.

>Fire, Poison, Electric, Ground, Ice, Dark, Dragon = 1,000
These types probably need a lot of meat or have very specific tastes and needs. There are also hazardous types and we need to account for potential damages to property these mons could accidentally cause. Their hazards are inherent to them and can occur more often than other types.

Once you have the type of your mon, you'll have to factor in both of its types(ignore if not-dual typed) and then the evolution combos.
>1st Stage, or Objectmon = 300

>Unevolving Pokemon, 2nd Stage = 500

>Fully evolved, 2nd Stage Dragon = 700

>Fully evolved Dragon, Psuedo-Legendary[combos with FE Dragon] = 1,000

>Fossilmons, Ultra Beast(yes, even if Poipole) = 2,000

Sample team:
Budget = 8,000
Dunsparce = 500 + 500 (1,000)
Rapidash = 1,000 + 500 (1,500)
Mr. Mime (Psychic/Fairy) = 500 + 500 + 500 (1,500)
Mantine = 500 + 300 + 500 (1,300)
Misdreavus = 500 + 300 (800)
Ariados = 1000 + 300 + 500 (1,800)
Total spent: 7,900
Leftover budget: 100