ok, example : you are playing a game with a friend. you agree on a 500 point match. you get your codex and look up the points of the models you have (one squad of guard is 60points for 10 models) you organize your army to what you thing would be a good force 1 guard=60 leman russ=150 etc.. than you play with that force n the table. everything is based on a point system to keep the battles as fair as possible. detailed point example: leman russ=150p sponsoon weapons(the ones on the sides)=20p front las cannon =30p armor plating =20p main cannon=50p total=270p as you can see if you are playing a 500 point match the leman russ will take up half because it is a good tank
well it is your choice, the necrons are ok but you have less choices. however have you seen the imperial baneblade? it is the ultimate tank in the whole game http://www.games-workshop.com/gws/catalog/productDetail.jsp?catId=cat180002&rodId=prod1080037&rootCatGameStyle=
however i think you will need the apocalypse book for the rules, i am not sure.
in a game of warhammer 40k you need a minimum of two troop squads and a head quarters. shock troops count as one choice. karskins are your elite troops, like commandos
