5th edition's Starter Set is decent to give you a feel for the basic rules, and outside players are not necessary. It is designed with beginners in mind, and is thus a good intro to the game. The starter set has an adventure in it that goes from level 1 to 5, while covering a lot of ground from a role-playing perspective as well as a combat perspective.
It's 20 dollars, but there's a high likelihood that most things outside of using the basic rules to create a character and joining the adventure league as a player are going to cost you more.
It does give you enough to work with to create your own campaigns as well, as the monsters in the appendix are varied enough for some play-room.
This is particularly advantageous if you don't have a lot of people in your current group and want to get going. If you just combine two groups, you might make the new group too big to manage reasonably. If there's only a couple of you it is easy and would likely be a great intro. If you have a single player you can draw in to play or DM that knows a lot about the game, it can certainly compensate on either side.
Presently the basic rules only cover character creation, however, WOTC has stated that they will be expanding the basic rules to cover some monsters and DM'ing advice as the core books get released. If you don't mind waiting a bit longer to start playing, then wait for the PHB to be released for sale (as that is when they are supposed to update the Basic Rules next), and download the updated rules. You should have some monsters and such in there that you can use to create your first campaign, free of charge.
If you are in a hurry to try it within the next 3 or 4 weeks, then by all means pick up the Starter Set, or find someone at your local game store that has it and wants to run a game. Ultimately, the decision on how to approach this is up to you. There is no wrong path to start the game.