Yesterday I had a weird urge that I haven't felt in a while, the urge to start with warhammer again. i dusted off my half painted miniatures and scavenged for ones that were not destroyed. I bought my first lizardmen 3 years ago, and to this day, I've been painting on and off to this day, yet I have never finished a miniature except for one saurus. Why? I have some obsession with finding the perfect blue hue, and when I can't find it drives me nuts and then I quit. ;P But that is beside the point, I want to learn the game and play it relatively casually. What I have right now: a package of temple guards a package of cold one riders a saurus old blood a couple of skinks and sauruses that stood the test of time. What would be the next step to get a working army? I'm guessing new skinks, but hell, I barely know the rules!
If you ask me, your next step should just be to straight up play a game. You'll get thoroughly trounced, but to some degree, you can only understand the rules by playing. Maybe play more than 1; do a couple of quick ones with different lists and tactics. I get what you mean about searching for the "perfect" hue/colour combination/theme, the one that's in your mind's eye. I think everyone experiences this to some degree. The only way I ever get passed it is to just do it - put brush to model, and don't stop until it's done. YMMV, but I've always found that I'm happy once it's done, no matter how different it looks to what I envisaged.
I agree with Mossy, nothing makes me want to paint / model more than playing a game, especially when my opponents army looks nicer than mine does (which is most of them) As far as what you should get next, lizardmen are so flexible there really is no one way of doing it. Safe bets are a slann since you already have TG, probably a skink priest, and more skinks or saurus. Just remember, we have no bad units except for razordons, and even they are okay in smaller games.
I'm with Old Mossy here. Play some games. You definitely need more Saurus and Skinks, to even make the army legal. Ask your opponent if they are ok with you proxying some models, in other words, using other miniatures or empty bases/pieces of paper as your troops. This way you can get a hold of the game and see which units are to your liking and how they work. Good luck with getting your army up again!