Im not to sure about what kind of jumping probably just show jumping... And I think my trainer has just said we are doing schooling Dressage. Im so new to all the show stuff :/
You can use the same tack and attire at both shows, if they're laid back enough.
For attire, I'd go with light tan or gray breeches, a white polo shirt or white long sleeve show shirt, and tall boots or paddocks and smooth leather half chaps. Black gloves are a nice touch, but not required. A velvet cover for your schooling helmet is a nice idea too, especially if your helmet is an "off" color or has a pattern on it. You shouldn't need a jacket for either show.
For tack, I'd ride in a nice dark brown AP saddle and matching bridle. You'll want a fleece shaped pad for the jumping classes and a square white quilted pad for the Dressage tests.
No leg wear for either show. If you school properly at home for both, she won't need boots for protection or support in jumping. None really provide much support anyway, even the "support" or "sport" boots, lol.
When you go to the shows, remember your above tack and clothing (wear something over your breeches and shirt to keep them clean), grooming box, bucket for water, treats, hay, spare halter & lead, spare bridle, spare girth and stirrup leathers, spare shirt, baby wipes (good for last minute horse, tack, and rider cleaning), bottled water for you, and some ibuprophen or tylenol (you never know, lol). Don't forget to pack a lunch and some handy snacks for yourself as well. You'll need your horse's registration papers, coggins or other required health papers, show entry papers and/or fees, and membership cards or papers (if needed).
To prepare your mare for the shows, take her on lots of trail rides. Work her up and down hills and over varying terrain at the walk and trot. That will help build her stamina and strength. In the arena, work on trot poles and jumping gymnastics to increase her coordination and strength. If you get her really fit, she will be able to handle just about anything
With her age, I would consider putting her on a probiotic and a joint supplement for preventative reasons. A good combo supplement is Missing Link + (plus). It has both probiotics and joint ingredients. That should help her stay strong and joints lubricated.
Good luck and have fun showing!