It's an easy ship to win with once you get the idea behind it. With that said, it's one of the most RNG-dependent ships in the game, but at least that mostly matters early on when you can reset relatively easily. Once you get a good start, it's an easy ship to pilot.
There are tricks that are really important with the Stealth B. If they have a combat drone, then you shouldn't cloak until you see it aiming at something really important (the weapons system being the most important). This can buy you time that might save your ship.
For upgrades the urgent upgrade is Cloaking level 3. Then shields (or alternative). Put the Zoltan on engines. After shields maybe a coule upgrades for the reactor. That means you'll have barely enough energy to do what you need to do, so turn off oxygen as needed.
Alternative: Don't get shields yet, but instead get anything that lets you kill ships in your first volley. I'm not sure which strategy is better. This way you can kill ships in one volley and start your road to weapons improvement. However, not having shields can be difficult because your 1-volley kills won't always work out, and when they don't you won't have shields. On the other hand, if you get shields, then it might slow you down so that you can't get 1-volley kills. Now you have shields, but fights last longer. Ideally you'll be able to achieve your shields need and offensive needs both in time to survive. Both strategies are viable, but which is more viable and by how much is unknown. My own strategy is to opt for whichever path presents itself to me first, in case I don't get another opportunity soon.
Ideally you'll make it through sectors 1 and 2 and get shields. From that point on your defense is simply a matter of upgrades to your ship, and you'll have all you need if you have enough scrap. Your next goal should be to get a weapon or system that compliments the glaive beam so that you can destroy ships for the sectors to come. At this point the Stealth B is no longer a bad ship at all, and can easily destroy everything if you pilot it reasonably well.
And if you die, then reset. Some deaths with the Stealth B are due to player error, but some are due to situations that are impossible to overcome. Eventually you'll get the good launch off the ship needs.
Watch a strong FTL player for a demonstration on how to use the ship to maximize your odds of victory:
https://www.youtube.com/watch?v=4i11nuh1_3E