The Bible
Ok, it is not exactly a devotional, but we at BestDevotionals.com always like to start with this one at the top of our list.
Open to anywhere and instead of just reading, look for who God is in the situation described etc. Get to know Him better as you read.
Let the Holy Spirit inspire you--it is not always as simple to do this as you might think. Here is a version we recommend for readability
and accuracy of things like various numbers (due to having older manuscripts available)--this is also less expensive than most devotionals!
Or if preferred, the King James Version which also has no copyright restrictions (if you want to write a song while you are meditating on His Word)
My Utmost For His Highest
The classic that never gets old. Oswald Chambers shares thoughts on a verse each day. One of the most popular devotionals ever.
(Insider note: this work was actually a team effort. After Oswald Chambers' death, his wife compliled his writings and her notes from his lectures and put together this devotional).
This comes in an updated language version as well
Oswald's complete works, though not inexpensive, make for wonderful reading or an excellent reference
The Purpose Driven Life
We highly recommend this popular book by Rick Warren, which is presented here as a Scripture based devotional to be read alone or alongside the book.
Here is the full book which is also great for a devotional time and focuses on the Lord

Get the Audiobook here: https://amzn.to/2KMVExm
For His Glory
Another devotional from an author of Scottish heritage (like Oswald Chambers), Colin Chalmers'
devotional has been praised as a blessing for all who have read it. Be sure to check out the 30 songs that go with it!
Here are the first 10 songs to go with the first 10 days

God's Wisdom for Navigating Life
Tim and Kathy Keller have put together a one year devotional based on the book of Proverbs!