Black and White is the favourite of the industry. 9 by 12 inches are the standard size. As you gain experience replace the older pictures with newer one. Do not wear jewellery for those prints, it takes the attention away from you. Tailor your portfolio for your strengths and the type of modelling you are doing. .
Comp card is a card with a few pictures on it.
It also has the information on how to reach modelling agency. It contains your statistic and measurements. The model pays for them and your agency will tell you how many you need to get started . See the photographer's portfolio. Keep that in mind.