There are many types of paper available in weights from 90lb to 300lb. 90lb is a light weight paper that will cockle alarmingly when wet, I would not recommend this paper for anything other than sketching. 140lb is a reasonably priced paper, this will also cockle slightly so requires stretching before use. 300lb paper is the most expensive but does not require stretching. This allows me to cut the paper to any size I require.
Some people prefer pads as they are convenient to use and easy to store.
There are three types of paper available, Hot Pressed, Not and Rough. Hot Pressed - A smooth paper which is manufactured by a method suggested in its name. A paper 'not' hot pressed with a slightly rougher surface. This type of paper is most suitable for the beginner. Once you have settled on a particular type and weight of paper you will be overwhelmed by the choice of manufactures different papers.