I’d say this depends on region, local ecology, the dragons motivations, and of course; opportunity.

Almost any dragon would suffice given the appropriate conditions.

If the dragon is your parent, than I’d think you need to read up on the personality traits of each of the Chromatic dragons, choosing the one that is most likely to have a non-violent relationship with your tribe. This would also depend on your tribes way of life.

• Are your tribesmen Tolkien goblins? Skulking in caves and using poison and superior numbers to overwhelm their foes? Maybe a Red or Black Dragon would be fitting.

• Was your tribe one that dwelled in a cold, mountainous region? That’s White Dragon territory.

• Are your tribesmen forest dwellers? Are they Wild goblins or organized raiders? Maybe a Green Dragon would be best.

I could keep going but I think I’ve blabbed enough.

You mentioned that you hadn’t fleshed out much yet about your goblins dragon connection; so I’d humbly suggest you do just that. Figure out how your tribe (our your goblin parent) would have come into contact with a dragon, and why that dragon would have agreed to help create/sire you.

I promise I’m not trying to dump on you; a Goblin sorcerer with dragons blood in their veins is, to me, a very interesting idea.. so it’s worth digging into.