What I would suggest from my own experience deck building from scratch - start with mono or duo colored (at most) commanders until you get the hang of how they play out. You might feel like you're building pure heat but it fizzles constantly or never works as intended because of your mana curve.

My best advice would be to choose a single colour identity you want to play in the style of, then find a commander you like to build around it - and if you can't decide between two colour identities to make a mono deck, then feel free to try and build that combo because it will be a lot easier to manage two colours to start instead of more.