Want to get in decent shape for martial arts club

[Rearden]

Why not focus on getting in shape before even joining the class?

The point of taking a martial arts class should be to learn the martial art not to be gasping for air as the techniques and lessons pass you by. Taking a martial art when youre not seriously interested, or just for the purpose of getting in shape, is in my opinion a big mistake which wastes your time and the rest of the class for folks who are there to learn.

Having no actual information on your current shape I'd guess that 2-3 weeks is not enough. Your strength training question depends a lot on what your level of physical capacity is now... saying you're not overweight is completely different than not being "skinny-fat", etc.

No matter who you are if you're seriously rolling with challenging opposition you ought to get a workout... if you're out of shape though rather than thinking about the position and what your options are you'll be stuck thinking about why you can't breathe.

Your comment about gassing out during a triangle choke makes little sense. If you had the cardio of a marathon runner you'd still "gass out" (more likely eventually pass out or be forced to submit) during a properly executed choke.

With your comment on being flaky in the gym... meh. Give us an idea what your conditioning levels are in terms of lifts, etc. Also... read the FAQ. If you did Rippetoe and some HIIT cardio seriously for some time you'd end up miles ahead of most entry level folks.