I'm not very knowledgeable, but I would guess futures? Cannot they get you massive leverage?
If I was trying to do this, I would consider futures.
Just for fun, I pulled up some ES data. It looks like ES Sep 2022 is around 3683, Sep 2023 is around 3759, and the index is around 3666.
Let's take Sep 2023 just to get in the ballpark of OP's original time scale. It's trading at a ~2.5% premium to the index. Presumably this wouldn't be an issue for OP since he's speculating for a large capital gain.
With my non-portfolio margin IB account, this contract requires 16K-25K margin (depending on initial vs maintenance and intraday vs overnight). Let's call it 25K, which is the overnight initial margin. Of course different brokers offer different margin, etc, but this is just to give a ballpark sense for someone who doesn't have their own numbers to work with.
1 contract of ES controls 50x3759 = ~$190K notional. (Sorry
@Overnight!)
So, let's suppose your account is $1M and you want to the "equivalent" of putting the whole thing into a 3x SP500 ETF. (It's not actually equivalent, for the reasons discussed earlier.) Then, that means you want ~ $3M notional. $3M / 0.2M = 15 contracts. 15 contracts requires ~ 15x25K = $375K margin. Done. Buy 15 contracts and you'll basically get the equivalent of 3x leverage on SP500 based on your full account value.
No discussion here of margin calls, etc. Occasionally I read scary posts on ET that reveal some people trade things they don't understand well enough and get themselves into trouble. If that could be you (not OP but "you" the reader) then don't just assume this post is the end of the story and please go learn more before you risk your capital.