Hey, I am Kenji. Welcome to saga. That is a really good question. I would say it is worth pursuing, I have had a blast so far.
As for ascertaining the power, offensive Genjutsu are essentially used to debuff the opponent, so you can follow the jutsu rules on what debuffs are allowed per rank. As a rule of thumb, I would reserve any Genjutsu that robs an opponent of an entire sense or faculty(blindness, deaf, paralysis, etc) for A rank and above but there is always room to negotiate.
Finally, try your best to implement creative and reasonably avoidable triggers, or a multiple means to escape the Genjutsu. If you app a Genjutsu that only requires eye contact, or the opponent be within a certain range, or some other difficult to avoid trigger, I would suggest doing your best to make that Genjutsu weaker for its respective rank.
Regardless of what specialties you choose, I hope you have fun.