You need a safer pair of boots! Anything with a lug pattern and an ill defined heel is an invitation to get hung up in a stirrup. You need a smooth sole and a well defined heel to lock against the stirrup. I hope your sister takes the time to demonstrate and HAVE YOU PRACTICE kicking out. Tight pants are neccessary to avoid chafing and your well broken in jeans will be fine. I would suggest a thin poly or silk set of long johns underneath. I would wear a hat and pack a good coat even if unused. Bring the gloves, but try riding without them first. Every horse has a different 'mouth' or steering coupled with the different 'hands' of each rider. The gloves may prove a hindrance getting the feel for one another. For gear always carry 2 knives; a one handed emergency use blade for wrecks and a good general use blade. A quality folder is O.K. Anything on a belt, including the belt can cause soft tissue bruising. Wallets in a hip pocket are garanteed sciatia! I outfit riders with a canteen, whistle, flashlight,folding knife,matches on their person and a quantity of paracord tied off to a saddlestring or buckle. Ponchos or space blankets are easily carried, but you better have the horse 'sacked out' or familiarized with them beforehand. Nothing scares a horse quicker than some flapping monster. A minimal first aid kit for the horse should carry a roll of bright vetwrap, a few large compress bandages and some Phenobutazolidin for pain ( but only if you are familiar with it's applications and dose). Forget all the salves and betadine. Clean water will flush any wound and doesn't make the DVM's job harder. This is minimal gear. Most people buy the biggest set of saddlebags they can find and then pack everything but cement inside. Lastly I would use a neck rope with the end tucked NOT TIED in your pocket. If you do part ways with your horse grab it and hold on. You will need an english noseband or western pencil bosal to rig it properly. The only thing else I can suggest is have fun!