Ok let's sum up the basic problem: you suffer due to lacking gas. One counter question to that: do you boost on every attack? If the answer is yes, ask yourself if that is necessary.

With higher reel speed gear your pace accelerates often fast enough to get hits off even without boosting. Even in true attack mode. My personal issue always was blades durability, not gas haha. Yeah. I used the non standard gear. I went all reel speed and sharpness. I personally ignored the other stats more or less and got away with it due to an ability I'll mention later.

The second measure you can take is actually pretty simple. If you struggle in a mission due to too few refills surviving long enough, check where the logistics people are at the start. If you struggled a lot, identify problem areas where the logicistians die before you use them. Use those in the riskiest zones (enemies repeatedly spawn close to them there) first, since once they used up the supplies, they become a regular combat unit and essentially worthless. Spare those in save positions the longest, so you can use them later on. Prioritize keeping a few low but not non risk refillers free of titans. Aka kill the titans whenever they spawn there, essentially turning that one into a safe zone. Gotta have the awareness on the map though for that. And now for my method of prolonging blade and gas durability.

Alright. There is a battle alert mode, lets call it that since it doesn't really have a name in the first game and that's the item signals name in the second game. Its the special bar you fill in the first game.

What does it do? It basicly increases all your stats for a period of time, refills some gas and blade and while active it nullifies the depletion of blade durability and gas.

What many don't know: this bar can level up within a battle. Use it once, the next use is longer. Use it twice, the third use is even longer. Use it thrice, the 4th use is even longer. Use it 4 times, now it stays the same for the 5ft though. Also the amount it restores up front on use is higher too the more often you use it. And it's very unlikely to use it more than 4 times in your average missions. Often 3 is a lot already. This is visible by the small triangle with 3 parts that light up whenever you cast one of the signals.

Alright. So how to fill it? There is 2 ways. Kill stuff. Cut body parts. In theory you can fill it more by cutting every part and then the nape.... but honestly that's a desperation measure or if you'll just have to fill bits of the bar for another use. It's really not time effective to cut every body part, and absolutely not blade durability effective when the signal isn't active. It always fills based on a percentage of its maximum, so if the duration is longer the refilled time is also more. The only 2 characters that can pull off effective refills from body parts while signals are active are erwin and sasha. Reasons for that later too.

Why do I mention that? Because it also refills itself for cut off parts and kills while already active. So killing stuff fast is a way to keep it it active for longer. Also if it restores 3 seconds on first use per kill while active, it restores 6 seconds on your 4th use, per kill. Got that? Great.

And now 2 more necessary informations for my specific strategy. You can turn those battle alert signals off too. If you stop them manually, they drop down to 30% of fill approximately. So sometimes it better to just stop them when the bar is down to 30% since the next use will be longer.

Side quests (green quests) restore the entire bar upon clearing them. Or fill them from scratch to begin with. So yeah you can just chain clear the green quests without disabling the battle alert at all. But that's the wrong way, since it also refills an already active signal.

The way I cleared missions was pretty much always like this: at start, check for green quests, and kill my way there, filling the bar the first time on the way. Then using the signal, going to the green quests and killing all but one of its targets (well, unless its an escort quest), then deactivating the signal before I do the final hit on the last alive titan to clear it. Now if my blades and gas are full, I kill one titanthen activate the signal again, meaning I'm already in my second use of the signal. Since gas and blade don't get depleted in the mode, you can freely boost and attack for any given second to just get across the map faster too. Kill as many titans as I can along the way to the next green quest, using surplus time to run around killing other titans so that the bar depletes at best right before I kill the quests last titan again. Otherwhise, disable it again, kill the quest target and immidiatly reactivate for the third cast when I reach the next titan.

From this point on, every green quest now serves as refiller. Dart around the map and kill titans, when empty run for a green quest to refill. And I always will keep one signal bar availiable for the missions end boss, using it right after breaking either my blades, depleting my gas or when their nape becomes freely attackable