When deciding about purchasing seeds it is best to think of where you want to grow to start with. If you are doing a indoor grow it is best to grow a Indica strain or a Auto flowering Ruderalis strain such as Lowryder. Lowryder and other 'dwarf' Marijuana plants grow no bigger than 2ft-3ft tall (sometimes a bit more) and 'flower' automatically. This means that they stay on the same cycle of light throughout their entire lifespan and will 'bud' themselves. In other words you do not have to change the light schedule from 18/6 (18 hours of light, 6 hours of darkness) to 12/12 as you would do with regular seeds. They will be finished in approximately 60-70 days from germinating the seed but will yield less than a regular strain. These types of plants have become increasingly popular over the last few years, and are ideal if you need to do a 'stealth' grow.
It is always worth paying a bit extra for good quality seeds from reputable seed bansk such as Sensi , Attitude, and Nirvana. There are hundreds of seedbanks so the choice is amazing, but if you want good results it is better to start of with a good established seed bank. Many of the the good seed banks will send out extra seeds if the ones you have purchased have failed to germinate & many will send free seeds with your orders.
Seeds can vary in price quite dramatically don't be fooled by some sites offering seeds for ridiculously low prices, if it's too good to be true it probably is. You can however get some good deals with the top seed banks as previously mentioned above, many offer '2 for 1' deals & free seeds with every order. Cannabis seeds usually come in two types. Regular & Feminized. What does this mean? A regular seed is a seed that will either produce a Male or a Female plant. The Female Marijuan flower is the one that produces the THC & Cannaboids that give you the 'high' feeling. Feminized seeds are seeds that have been bred so that they are highly likely to produce all Female plants. Although this is true they sometime have some 'Hermie' traits. This means the palnt will show male & female traits & can pollenate itself which will dramtically reduce the amount of bud that is produced. It will also produce seeds.