I had quite similar dilemmas. The main force behind what I choose to buy is a combination of model beauty and monetary cost with a sprinkle of tactical value added. I love the TG models, but they are such a waste of points that I've opted to keep them sitting there, taunting me, on the shelf until I have my slann. To replace them in my 1k army I bought a pack of skinks.
I'd go for a mix of blowpipes and javelins. From all accounts each has their use and both options are worthwhile. I personally run 11 skinks with javelins to go with a kroxigor (ranks at 5x3), with the rest being blowpipes, allowing for two skirmishing units. You could go for one unit of 11 with krox, one unit of 10 ranked javelins, and one unit of skirmishers so that you get to try everything, as 10 plain skink cohorts serve a different role to 11 with a krox. The krox unit can take out enemy light support units, the cohort is best used for redirecting (as they are half the price and less of the krox unit) and marchblocking, while the skirmishers are the best option for harassing, shooting unarmoured or large targets, marchblocking and can redirect well too. I'd take the skinks over the saurus as 20 (I'd prefer using only 18 for 6x3 with spears) is plenty for 1k, more and you end up with a huge chunk of your army being low movement.
I actually got one scar vet CO as general and one scar vet on foot (chakax model) to act as BSB in the spears unit. If you want to go for only one, I'd choose the CO over the one on foot.
To be honest just getting a hero, the battalion and whatever paints you need should tide you over for a long while if you want to play only once things are painted but however you choose to do it I'd get the battalion and maybe some skinks, play a few games, (then get the extra skinks if you hadn't already), then decide what to expand with having played a bit and read through the book thoroughly. The things to then consider with your new-found experience for 1k would be terradons, a krox (or three if you want a unit of them), salamanders/razordons, or another hero (probably BSB, skinks priests cant do much alone). After that, like I said before, the best path to 1.5k would be another option from that selection plus one of the stegadon choices (almost certainly EotG, especially if you're planning on a slann).
After that if you're planning on a slann another battalion actually makes a lot of sense. The battalion roughly costs the same as a box of TG and a box of saurus, plus you get another unit of skinks and enough COR to mean that you actually have the option of switching every once in a while, running your scar vet as an oldblood and using 3 units (of 5, 5 and 6) of cold ones! That's how I have it planned anyway.
