Speed

Your creature's Speed should be 25 feet if it moves like a human. Beyond that, you can set the Speed to whatever makes sense. Remember that the creature can move up to triple this number if it spends its whole turn moving, so if you want the PCs to be able to chase the creature, its Speed can be only so high. Most creatures should have a ranged attack, fly Speed, or other way to deal with flying PCs, speedy PCs, and PCs with more efficient actions that let them engage and retreat more easily. This includes creatures converted from Pathfinder, where PCs can only fly at higher levels (see Anachronistic Creatures for more information.)

Creatures can have climb and swim Speeds at any level. While you can give your creature a fly Speed at 1st-level, as most PCs should have ranged options available to them, it's better to wait until around 3rd level (when PCs have enough feats to support those ranged attacks and access to items like jump jets and jet packs) to give your creature a fly Speed if it also has ranged attacks or another way to harry the PCs from a distance indefinitely.