It's preferred. I mean, I won't say you absolutely have to. As I said, though, if it's because you're unfamiliar with it, come up with just two Ignis monsters for your first few Duels. For example, Yusei used "Junk Warrior" as his only Extra Deck monster for quite a while except for a couple of times with "Nitro" until he got "Stardust Dragon". Of course, there were others that he'd occasionally use, but for the most part, you could just stick to one card for a while and just throw in a couple others where necessary.

However, if you wanted to make use of Mono-Tuning and/or a little bit of general Synchro Summoning in some form, that would be awesomes, too.