Hi - we have worked with a number of subscription box services. I have over 15 years helping startups in various industries and spaces. In terms of best channels it depends on the company. How long have you been in business? I would need more detail to give a proper answer but here are some avenues that might work. 1) I would do a big launch announcement and use a key influencer in the space to host it 2) I would send the launch news to the top tier media outlets in your market and in national markets 3) Put resources towards a great short shareable video that explains what the UVP of your service is 4) Find a journalists or writer friend and take them for coffee and brainstorm 20 different press angles for your business -- earned media is one of the best ways to acquire customers 5) Put effort into your content marketing strategy and specifically instagram -that's a great place to market to women. In short you need a combo of:
1)Earned media
2) Owned media (social channels)
3) Paid media - sponsored posts, boosting FB ads,etc

If you're limited on resources focus on the first two as they don't cost you anything but your time. If you have the money consider bringing on a consultant or agency to help manage and execute some of your strategies. There are no 'best' channels - every service, ecomm and business is different so requires a different approach Good luck and if you want more info I'm happy to hop on a call.