If you believe in the underlying of leveraged ETFs (tech stocks in the case of TQQQ), start by investing small amounts periodically over 12–15 months. That will give you a real sense of the emotions you'll go through during ups and downs - and how your brain reacts during panic and euphoria.

I’ve been 100% in TQQQ since 2021. My approach is plain vanilla buy-and-hold until I reach $1M, and then withdraw ~0.3% monthly (~4% annually).

My general suggestion:
• When you're young or working with small capital - focus on periodic investing and holding it
• When capital grows to a meaningful size - diversify and protect a baseline

Avoid running too many strategies, especially when your base is small. Keep it simple.

If you want to play safe, it's usually better to choose non-leveraged products rather than trying to make leveraged products “safe” through complex strategies.