If you want to get a great deal on a Nintendo 2DS, there are actually a lot of great options. Here I'll go over some tips that can help you find what you need for a discounted price.
The 2DS is basically just a slimmed down version of the 3DS system, and it cannot display in 3D. That's okay, however, because all games do not require you to use this feature anyways.
Save money by trading in your old games. If you are tired of a few games you have and don't want to keep them around, you can try selling them online through a website like eBay and then save that money towards a 2DS. From used to new you'll spend from $50 to $100 on the console which translates to not having to sell many games.
There probably are going to be sales when the holidays roll around. You can also expect the system to go down in price as they release more updates to the better hardware. For instance, when the New 3DS came out, the 2DS dropped in price. Even if you're not able to wait for the holidays you can generally find a deal if you shop around a little at local and online gaming stores.
Put up an ad on a website like Craigslist. They will let you put what you want in their games wanted section, and people will be able to email you with deals. Don't ever buy anything from someone or trade to them without testing the system first. There are multiple built in pieces of software on the 2DS so have them meet you in a public place and boot up the system and play it for a few minutes to make sure it actually works properly.
1 - http://www.polygon.com/2015/8/20/9181487/nintendo-2ds-price-drops-to-99-99
2 - http://www.craigslist.org/about/help/how_to_post