So, don't get too caught up in strums, as the best approach is to start any new song with this basic down strum. Then, hit the strings on the way up as well, the down-up strum while counting "1 and 2 and 3 and 4 and." This way you are making twice the amount of sound with the same hand motion, giving you a little more movement and fuller accompaniment to a vocal line (melody).
Some instructors spend too much time talking about theory and other things mixed right in with the middle of the song instruction, irrelevant to actually learning the song, and then fly way to rapidly though the chords, progressions and riffs, making learning difficult and multiple rewinds and replays necessary. (Example; Behind Blue Eyes by Mark Olesky. )
As a beginner, it is best to avoid making a pawn shop, flea market, or yard sale purchase unless you are shopping with somebody who has experience in purchasing a guitar. Having never purchased a guitar, you may not know what to look for in terms of damage or guitar quality. With that being said, a local music retail shop is your best bet. You may also shop online with a reputable company, although be sure to review the business’ return policy.