Thought I would give a heads up to what I regard as a good app.
For me a good app has to work as expected, do what you want it to, have the ability to configure things so that you can make the experience your own and be cheap enough to warrant consideration.
There are a lot of really good apps out there which are worth spending a few pennies on but the one I am thinking about is Textra.
Textra SMS iOS Emojis as well as allowing various levels of configuration. Most importantly the app is free to try and 61p to buy, so it will not break the bank. The app automatically adds photos from your Google account to match the people who are texting and there are options for quick compose and default signature as well as the ability to delay sending something. All of these features and the ability to have a dark background or light one make the app a winner in my book.