When starting to pick out stationery for your wedding the first thing you have to figure out is are you going to go with a bespoke invitation or a pre-made design? This is really going to depend on what is important to the couple and what your budget is. So lets breakdown the pros and cons of each.
Bespoke Invitations typically have custom illustrations, calligraphy, gorgeous paper and ribbons tailored to the invitation design. They are designed by a professional stationer designer who can help you with every little detail when it comes to stationery. These invitations tend to reflect the event and the couples personality perfectly because the invitation is being designed for the couple. Lets face it they end up being absolutely stunning, one of a kind, and come with all the extras. Sounds amazing right? I mean they really are but the stationer also spends a lot of time designing and producing such a beautiful invitation suite which costs money. They will most likely end up costing more money than a pre-made design. However, a lot of stationers do have little tricks in their back pocket to help keep costs down if needed. So if this is something you are interested in I would try to contact a stationer letting them know your budget, what pieces and quantity you would like to see if they would be able to work with you.
Places like Bella Figura, Smock, or Crane have some very nice designs to pick from. They have options to get some add ons so you can have the envelope liners and the ribbon. They also let you pick out the fonts and inks colors giving you a little bit of customization. If stationery is not a big priority to you and you want a simple invitation with a font this may be the best option. They are fairly easy, quick to get ordered, most of them are printed on nice paper or have an option to upgrade the paper, and they can be more cost effective. The main downside with the pre-made invitations is they are a bit generic because they have to appeal to a broad range of couples and depending on how popular the design you pick is your guest could have already gotten your invitation from another couple for their wedding.
Let me know in the comments which direction you went with your stationery!