How much are you hoping to get for them? You might be asking too much.
In bundles I'm looking to pay under £2 per item. Preferably around or less than £1 per item. Because I know that there will be things in there I like and things I think are naff and will pass on/charity shop. If you label your bundles so this is clear you may get more takers e.g. "40 item bundle £25". I would also sort according to gender, size and season. "Boys' 20 piece summer bundle 0-3 months" sells much better than a random assortment of clothing. You can also direct people to your neighbouring bundles e.g. if you have a 3-6 month one as well. Add "Perfect for babies due Feb-May" to entice pregnant mums who haven't necessarily thought ahead to the fact their spring baby will be 3 months old in summer.
I find the best for bundles are local FB groups, the smaller the better.
If you have photos of items individually, you may have luck on FB if you say something like "£3 each or £10 for all" - I am prepared to pay a bit more per item if I can pick and choose which items I want. It's also best if I'm local so I can pick up and don't have to add on postage which brings the total cost per item up. Jumble sales, car boots, nearly new sales and so on are usually the best places to sell items indididually - but bear in mind the absolute cheapest price you can get things new for - supermarket prices for example and within multipacks - for example, Asda at the moment in their baby section have:
4x shorts for £9 (so second hand = £2 each)
5x vests for £7 (so second hand = 50p-£1 each)
3x sleepsuits for £11 (so second hand = £2-3 each)
5x t-shirts for £15 (so second hand = £1-2 each)
3x leggings for £9 (second hand = £2 each)
So you can't expect people to pay more than this for second hand things, even if they are Next, unless you are in a Next selling group (in which case, have a look at how other people are pricing things) or have a very exclusive Next item that was sold out immediately and people are fighting over (then ebay it, use the exact title from the Next online listing, and ASAP). If it's character branded or label (adidas etc) then you can safely add £1 or so onto the price, but this tends not to be true for tiny baby stuff, more for toddler 2y+.
For single items ebay used to be alright, but is overloaded now with the exception of those specific sought-after items. I do buy clothing on ebay but I tend to be the only bidder these days and get it for the minimum, whereas 10 years ago when I used to buy it I'd often get into bidding wars and pay up to £3-5 per item.