Selling in Local FB Groups

I have some merchandise that I acquired specifically to sell locally, and I planned on listing them on craigslist but also wanted to supplement it using local FB groups.

I planned on creating a fake FB account to do this, but would there be any advantage to buying an aged account with friends as opposed to creating my own fake account and buying friends?

I was also thinking that creating other fake accounts and liking/commenting on my original posts might be helpful.

Are there any tips you guys can give to increase sales?

Tips? Not anything that you don't already know. Use proxies. Dedicate certain proxies to certain accounts. Make the timing of liking/commenting seem legitimate. Have both male and female accounts. For sales you can look into:
How to win friends and influence people - Dale Carnegie
Secrets of closing the sale - Zig Ziglar

Is it essential to have proxies when only running a few fake accounts?

Any times that are best to post? I have noticed that during high traffic times the posts tend to get buried quicker, and I think it might actually be better to post during less active times so it stays up longer.