Believe it or not you can winstreak on hard consistantly if you're good. General FTL tips -
Pause the damn game. A lot.
You need to think of the entire game more or less as a mission to get as strong as possible for the flagship.
Never, ever, ever, ever, ever, ever leave a sector earlier than you need to. The point of the game is to build up your ship, if you skip beacons you are basically playing at a higher difficulty level because you will have less scrap to build up your ship for harder sectors/the flagship. This is the most common way I see people shooting themselves in the foot in FTL, it's a horrible idea.
Fire weapons in volleys so the projectiles arrive at the same time to better deal with shields.
Look up a list of what weapons people think are good to get a rough idea of what good weapons are. When purchasing new weapons, think of how they will work into your "volley", weapons with cooldowns that don't line up aren't ideal.
The enemy will always fire his weapons on cooldown into a random room. Outside of the flagship fight, the enemy actually uses the same weapons as you, and you can gather which weapons have which cooldown over time.
Killing a ships crew without killing the ship itself nets extra rewards, although if you take extra damage this quickly negates that. Teleporter ships can make loadsomoney.
Taking damage and especially losing crew sets you pretty well behind for the rest of the game. If you never lose crew, you likely won't need to buy crew, and can save yourself hundreds of scrap.
Vs flagship (In AE)
Want to make life easy? Play non-AE and fight the easy mode flagship. It's the easiest flagship fight in the game.
Pause a shitton
The missile and shields systems are the most important to take down.
The enemy crew does not come back between flagship phases. All the crew you do not kill before stage III except one will board your ship. If you are having an easy time with a flagship phase, you definitely want to try and snipe enemy crew members with your weapons. The ideal is to leave one crew member alive in the middle of the flagship, if all crew is killed the flagship automatically repairs itself which is more annoying than dealing with one crew member. One of the most hilarious strategies in FTL is letting the enemy crew board you, and then FTL jumping away to abduct and murder them.
Cloaking level 1 good vs flagship. With cloaking level 1 you just time it to dodge flagship power surges (or missile volleys in stage 1) and you can often but not always cloak multiple power surges this way so long as you don't stay cloaked after the surge is over. There is ways to take advantage of cloaking 3 in the flagship fight, but due to issues with a longer cooldown than cloaking 1 it's a bit more complicated to take advantage of.
If you don't have cloaking, you want drone control with ideally two defense drone I (better than the mark IIs) deployed on opposite sides of your ship, drone control systems tend to be better on smaller ships. Missiles can easily fuck you up through 4 layers of shields, you usually don't need BOTH cloaking and drone control though, but you definitely want one or the other. If you don't have either, pray, and get a shitton of points in shields and engines.
level 3-4 shields/5 points in engine/6-8 in weapons should be happening every game. More crew is always useful.
Level 2 oxygen (for phase II in AE) and level 3 doors (for phase III) are very good quality of life purchases, although you can win the game without them.
In AE phase II, don't fuck around with the boarding drone, send 3 guys to kill it instantly. Opening up your ships internal doors can give you more time to kill it before the room is emptied of oxygen, although the entire damn ship will run out of oxygen really fast and murphys law dictates the next missile will land on the oxygen room (which is another reason oxygen level 2 is good)
In AE phase III, level 1 mind control can negate the super annoying level 3 mind control the enemy ship has. This isn't to suggest picking up mind control is nessecary, it isn't, but if you have it do this.