And "startup" doesn't have to be 3-4 people. I remember trying to recruit an engineer when Google was maybe 150 people. I tried to convince the engineer that Google was doing well and it wasn't as risky as it looked, but she decided to go work for Siebel instead.
In other words, don't waste money/time/effort on things where you can't make a big difference. Find an area where you can have a lot of leverage or expertise and put your chips there.
Hindsight being 20/20, for every "She turned down being employee number 151 at Google to work for Siebel LOL" story, there are 10,000 (maybe 100,000) "I took a chance with Pets.com and they still owe me 6 months of back pay" stories.
When you're playing the stock market, going for single stock picks is a really bad idea. Diversification -- even modest diversification of a few companies, but preferably in different markets, hugely reduces your volatility risk. Tech is highly volatile -- investing in Microsoft, Google, Apple, Cisco, and Oracle would be nominally diversified (and there were a couple of huge winners there over the past 10-15 years), but you also incorporate a large sector risk.
When you're working for a start-up, the key is that you're moving beyond simple punch-the-clock (or per-month) income. You're not just earning a wage or salary, but there's some upside potential in the company itself. Of course, that is a tremendous risk, and the odds are good that any given company won't pay off. There are also multiple ways in which that bet is rigged, including options vesting and the fact that your employer can effectively claw back your earnings by firing you (for any or no reason, at any time) before your options vest. You've also got to have the cash to actually buy out your options.
There are other ways of building equity, one of which is to invest in your own business, venture, real estate, etc., outside of your employer. Buying investment rental property, for example.
The key though is that you want to move beyond just "I'm a wage / salary owner" status.