I have, uh...fairly expensive taste when it comes to clothes, and my kiddo's clothes are no exception. And I'm terrible at planning purchases - buying next year's coat when they go on sale at the end of the season, for example. That is almost never me. I typically wait until, say, R has torn holes in the last pair of pants he has....and then I shop. Needless to say, I often miss the sales.
I try to make up for my crazy be being very picky about what we DO buy, and keeping clothes to a minimum in general. For example, each boy has one drawer full of clothes. ONE. One drawer for all pants/shorts, shirts and sweaters. (Other items like socks, underwear, swim clothes, soccer uniforms and winter gear are stored somewhere else and I do swap out clothes in their drawer for seasons.) I feel like we're always doing laundry around here, and switching to this system didn't seem to impact our overall laundry load very much.
This system works because I can then buy the pricier items I love....because I'm only buying a few things. And honestly? My picky toddler wants to wear the same thing everyday anyway. And I find that something like a sweater - which he pretty much only wears when we're leaving the house, virtually never gets dirty. (Not that we're all that picky about dirt around here....his jeans are pretty much ALWAYS dirty. But they're designer (Joe's Jeans) so I tell myself that the dirt goes with the premium wash, LOL).
Additionally, I stock up on plain Target tees. You can find these babies on sale for about $2. That leaves me free to buy more expensive pants (I love Joe's Jeans and plaid Nano pants), sweaters or sweatshirts (we love Splendid's sherpa hoodie), and cute shoes (I swear by Uggs for toddlers). In the winter I get less expensive pea coats (from Gap or Old Navy) for going out (and these are widely available on ebay)...but I do splurge on Patagonia's Baby Down sweater for everyday use (not as crazy as it sounds - see here: http://www.aintnomomjeans.com/2010/07/go-buy-now-patagonia-baby-down-sweaters.html)
And I do shop secondhand. When I have time. But it's hit-or-miss, especially when you are keeping purchases to a minimum. I like to befriend the store owner, and make sure she's clear on my preferences. They'll often be willing to call when they get new stock that looks like your style.
I do have one little sales tip: Nordstrom's Anniversary Sale. It happens each summer, and typically includes Joe's Jeans for toddlers and kids on super-sale. I stock up. Also, I'm a big fan of buying jeans a bit big, and rolling the cuffs. When he grows, I unroll. When he grows again, I re-roll, add striped socks and call them man-capris. R will literally wear a single pair of jeans for years.
Lastly, R has just started to tear holes in the knees of his jeans. This is from constant "zooming" on his knees with his trians, cars, etc. I'm currently looking for some cute, old-school patches - a bunch of these could look really cool, and add new life to his jeans. (Although I have no problem with destroyed denim - we both wear it, LOL!) Anyway, I found some great patches on Etsy - stay tuned to Ain't No Mom Jeans - I'll post an article letting you know how my little experiment goes. :)
ps. I support, whole-heartedly, toddlers and kiddos dressing themselves. See the link below.