Will you be creating your own artwork or using clip art/photos? And do you have time to learn a whole new program? Manga studios is great for creating original art. Indesign is used by a lot of graphic/magazine designers for designing an overall poster/page/etc. They'll both cost you though.
Manga Studio 5 is currently on sale for $47.99 (normally about $80 I think) Adobe indesign is available as a free trial, not sure how long it lasts though. It will set you back a few hundred quid to buy, can you sign it off as a business expense?
I expect you'd need to look up a few tutorials to get yourself started, I managed to teach myself the basics of both within a few weeks, due to my own strengths and how I use it (for posh event guest lists, html email design) I find indesign easier. The learning curve can be quite steep, but if you've got time to play about with the tools without a looming deadline you'll soon find you can create stuff that looks pretty good.