I am also in accord with everyone else here.
Start with something non-magic first. it can be a little tricky to a beginner.
When i first started Lizardmen, it was fuuuuuun. (a bit crazy) but fuuuun.
i enjoyed starting off with the warriors and skinks. it gave a nice taste to how lizardmen over-all work. a solid, hard hitter such as saurus, and a quicker, more maneuverable unit of skink skirmishers.
after that, i decided to go with some more fast, but powerful things, like the Cold One Cavarly.
as my love for the scaly's grew, so did my aspirations.
i enjoyed more and more units, and the destruction they wreaked on the field of battle.
so, in wrapping up, go with what you think looks good, and what suits your personality and playing style.
Do you like solid walls of awesome? go with Saurus.
do you like fast and pwerful? Cavalry and beasts.
Fast, agile, and shooty? Skinks are spawning favorites.
so just go with what you like, then work on what works for you.
I suggest that battalion box as well.