A 15 page essay in high school? That's an ambitious project for sure!

So first step that you want to take - give yourself a thesis statement. This doesn't have to be final, and honestly, it can change. But you need a starting point, so make sure you give yourself one. A thesis statement is best when it's simple: what are you gonna write the paper about? What are you trying to say?

For a random example, you could start with the thesis that "The optimates and populares shaped the political sphere of the Late Republic."

And that'd be just fine to start with! It gives you a nice platform to move from that directs your research. This statement might change as you go. It might not, and you might be able to double down on it. But give yourself that direction - if you don't have it, you're going to do the equivalent of drinking from the fire hydrant. You'll explode with info, you'll try to put as much as you can in the paper, and it's gonna meander and make a mess.

Second step! Start the research. You're armed with that starting point, which is an enormous help. The research stage is honestly the most time-intensive one - writing afterwards is the easy bit. If you have access to a good library, that'll help enormously. If not...well, it's possible to make do with Google books, but it's not gonna be top-tier. Learn your library, and if you get lost or confused or aren't sure where to start, ask a librarian! They're magical human beings who generally love helping. Ask them questions - they know how to research, and, even if they don't know the topic at hand.

Substep to step 2: know what an academic book looks like. If you pick up Tom Holland's Rubicon, for example, you're gonna get a very skewed, very misinformed view of the topic (because he has a specific agenda and he takes "artistic license" where he feels like it to achieve that agenda). On the other hand, if you pick up a book by an actual historian (read: not Tom Holland, Jared Diamond, etc), you'll get a far better view of things. This results in not only a better paper, but a better you, since you have a far more informed opinion.

Start with a major book that covers the field. If you can, look for major university publishers: Oxford, Cambridge, Routledge, etc. They generally put out some fantastic overview books that can catapult your research - because you're not just using the book for the things that the authours write about, but you're using their sources as well. Historians will always cite their sources, and if you want to know more about a specific topic like...say....how the populares might have used certain forms of propaganda to their advantage, then you'd follow the paper trail when a historian mentions elections or perception. The first source has already (generally...) done the vetting for you, so you know that the places that they're linking have some authourity (read: not Tom Holland. Did I mention that I can't stand him as an authour?).

So, for example, let's say you start with a book like The Cambridge Companion to the Roman Republic. Well, the table of contents has a couple of interesting chapters - one titled "The Crisis of the Republic" and another titled "Spectacle and Political Culture in the Roman Republic." Both are (spoiler alert) written by two incredibly brilliant professors, one of whom still works at Princeton. So you're starting with good material here, and the book itself gives a great overview of the period. Again, this is just a random sample of a book that might be relevant to illustrate a point, especially if you don't know much about the topic at hand. Start big and use the big things to work down. If the big thing is an actually good starting point, it'll point the way.

If you'd like some more guideposts, I can offer a couple of suggestions, but /u/LegalAction is far more well-versed in the topic than I (and might be able to offer far better source material!). The trick with research is to budget your time appropriately - it takes time, and a good paper is going to have a decent amount of sourcing backing it up. Make sure that, if you make a statement, you have a reason for doing so. If you're making it up, there's a decent chance that you're wrong ;)

Regarding the structure, it ultimately depends on your thesis and your personal style: if you want to split it 50/50, that's possible, though I personally believe that the Late Republic is such an interwoven mess that it'd be a bit of a mistake to try to seperate them that drastically. Ensure that each paragraph is relevant to the topic. When in doubt, imagine the thesis statement at the end of the paragraph. If it fits? Great! If not? Add a sentence to explain why what you just wrote is relevant.

Best of luck!

I would figure out how to narrow your focus. The thing to remember is that the Roman sources deploy these terms irregularly across time, and these "factions" were not "factions" in the sense of a group of people that met regularly and had shared goals; they were much more amorphous and, to my mind, seem to indicate trends in political participation. The other reason why you want to narrow your focus is that fifteen pages seems like a lot to you, but it's not nearly enough to explain these two groups. I would pick the aspect you are most interested in: i.e. the Gracchi, Cicero, Marius and Sulla, the Sullan dictatorship.

Hi - we as mods have approved this thread, because while this is a homework question, it is asking for clarification or resources, rather than the answer itself, which is fine according to our rules. This policy is further explained in this Rules Roundtable thread and this META Thread.

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