You should try to get the mulch down in late winter/early spring before the spring/summer weeds start sprouting.  A 2-3" layer of mulch is best.  Mulch type is usually a personal preference.  Shredded hardwood mulch does a good job suppressing weeds.  Triple-shredded hardwood mulch is nice and doesn't usually have chunks of wood in it.  As the mulch decomposes, it adds nutrients to your soil.  Generally, you need to add new mulch to your garden beds every couple of years (some people add new mulch every year).  Weed-pulling is an Olympic sport in our area so don't be surprised to find weeds growing in your mulch.  Many things can spread weed seeds (wind, water, birds, etc.).

Here is some information on mulch.

Mulches-Brochure.pdf (ncsu.edu)

Mulch | Home & Garden Information Center (clemson.edu)

We cannot recommend places to purchase mulch.  If you have a small area, you can purchase bags of mulch at a big box store or a local garden center.  For large areas, search for "bulk mulch for sale" and you'll find numerous places that sell mulch in bulk.  The City of Raleigh sometimes has a "buy one get one" special on mulch but you have to pick it up yourself as they don't deliver.  The amount is usually what will fit in the bed of a pick-up truck.  You might want to use social media (Nextdoor, Facebook, etc.) to get recommendations on places to purchase mulch.  Some places are better than others and getting recommendations is always a good idea.

You don't have to wait a certain amount of time to plant in your new garden bed.  You may want to wait to make sure none of the shrubs/bushes regrow as can sometimes happen.  You may want to consider adding soil amendments to help enrich your soil.

Making the Most of Your Garden’s Soil | N.C. Cooperative Extension (ncsu.edu)

Soil Conditioning – Establishing a Successful Gardening Foundation | Home & Garden Information Center (clemson.edu)

Soil Testing and Choices of Amendments | NC State Extension (ncsu.edu)

Since you are new to the area, you might want to check out the pollinator garden in Chatham County for ideas on pollinator plants.

Chatham Mills “Pollinator Paradise” Garden | NC State Extension (ncsu.edu)

Thank you for contacting Ask Extension.  Please let us know if you have additional questions.