Stop leveling Martha after 1st ascension?

Well I'd level her to max level anyway, even if I don't plan to use her.

Depend on you. I even strengthen her to get her 3rd skill.

However, even though her 3rd skill is still a decent supportive skill.

If you want to only use her 2nd skill then defeated. Fine, 1st ascension is your choice. I am not Martha fan, but you know you can equip Taunt CE for her if you want her to be defeated in few round. But it is NOT "Since the rest of her kit isn't that good".

Her strengthening quest will give you a free SQ, but you'll need to Ascend her 4 times for it, and as WC said, her third skill is pretty good. She'll also have her interlude at ascension 2, also gives free SQ.

Her 2nd and 3rd skill are good, wdym with "isn't that good"?
At least FA her and make her skill 4/4/4 for the minimum.

I am biased here since I've been using Martha Rider for a majority of fights including boss battles ever since the Accel Zero event, but honestly, I do she is a very good servant. However, if she isn't a priority to you, then I still think you should level her up a little so she is a bit more survivable. It wouldn't really help if she dies before you could use her skill to clean debuffs