[gls2ro]

You are probably asking what frameworks to use. But I suggest you should first use Sketchapp or Adobe Experience Design (at least these two I used and liked a lot).

They allow you to do some UI mocks/basic design with very little effort.

You can find and import in them Boostrap templates providing you with all the elements you need. Then the next step I suggest to do is to pick the basic colors you want to use for normal text, action buttons ... This way you will make sure that in your app you will use only those colors providing a consistent color scheme.

And then you can start to design your interface. Both apps provide simple tools to use and with very little learning curve for doing simple design.

For me (even if I am not a designer) doing this helps me focus on understanding how the elements that I want to build integrate with each other on UI side. And also forces me to focus on using the same elements and the same colors.

For both apps you can also find a lot of free designs provided by various authors from which you can inspire.

You can also browse https://dribbble.com or https://www.behance.net to be inspired by designs that you like.

[iDemonix]

I really struggle to design things in a design app. If I have to design something with Bootstrap I just browse for a bit of inspiration on Dribbble then start coding.

I'd love to be able to design things in PS or Sketch but I find it takes 5x as long as it'd take me to make something by hand.