Apologies if this has been answered, but
How many parties can you have in MTG? I’m aware that a party consists of 0-4 so cleric, rogue, wizard and warrior.
But if I have a full party and say another 4 creatures, (1 from each) does that mean I have 2 parties or is the maximum allowed 1 party?
There isn't a card nor an entry in the rules that mention multiples parties, therefore the number of parties you can form is irrelevant.
Also, rule 700.8a state s
The calculation of the number of creatures in a player’s party is performed automatically by the game and results in a number between zero and four. Players don’t declare which specific creatures they control are in their party.
The party mechanic doesn't care about the individual creatures but cares about the diversity in your whole pool of creatures.
One per player.
The text of rule 700.8 makes this clear (emphasis mine):
700.8. Some cards refer to the number of creatures in a player’s party. A player’s party consists of up to one creature that player controls for each of the following four creature types: Cleric, Rogue, Warrior, and Wizard.
Throughout 700.8, the party is always referred to in a one-to-one relationship with the player. A player has exactly one party (even if it's empty); phrasings like "a player's party", "that player's party", etc. would make no sense if they could have more than one.
Despite the common meaning of "party" and the flavor it evokes, party is not a mechanic for grouping creatures into discrete entities, it is a count maintained by the player who controls those creatures.
