As another poster mentioned, mods. It’s tough when you can’t afford to buy 3 refreshes a day, but do not neglect mod farming. Rex lead can reduce the need for speed to a certain degree, but you still need the right mods for the right squad members.
If nothing else with speed other than to determine the order they go in. With the 100% drop rate, none of your sims will be wasted, but you will get a lot of grey mods. Don’t waste credits leveling these unless it’s a 5* speed primary arrow or in some cases a 5* crit damage triangle, or a 5* potency cross.