Simple Routines to improve your Martial Arts
Simple routines like regular long slow distance running increases your endurance during sparring and makes your kicking faster. Plus its free and requires only a good pair of trainers.
Finger press ups - increases your gripping strength for joint locking, makes your upper body stronger and punches faster.
Shadow box - Practicing combinations makes them automatic when sparring.
Stretching - full body stretching gives you increased movement, focusing particular on the legs makes your kicks higher and less effort. Also its great for massaging muscles.
Various exercises like sit-ups, leg raisers.
Chi-Gung - builds chi
Meditate - develops your focus
Most of these can be performed in a very limited space. With a bit of imagination there are loads of things you can practice with limited space/funds to improve your martial arts.