Tl;dr: download assembly immediately
I struggled with "Sketch" on the Mac and had almost given up on vectors when I found assembly!
Lets you save as PNG(transparent or non), PDF, or SVG.
You can then use other Pixite apps (like Shift) to add gradients and patterns to your vectors.
Oh! And download imaengine - take pictures and make them into vectors! Then you can open it in assembly (slow if complex) and edit it.
Seems like the inspiration section is stagnant. But the assemblyapp Instagram is current
Hopped up on iPad about Vector & SVG Maker - Assembly, v1.4