Here's some tiles I made myself, you're welcome to use them if you wish, at least to get you started. The roads are in the same style as SimCity2000, but they're not copied from that game, I made them myself from scratch (no copyright issues).
There's tutorials online, I suggest looking up tutorials on making tiles with Blender. I am not much of an artist either, but creating 3D renders is easier and perfect for isometric tiles. Another good program that helps create them easier is Inkscape, there are tutorials for it as well.
I organized these tiles in a binary fashion. So the north corner is 1, the east corner is 2, the south corner is 4 and the west corner is 8. To get the tile number you want, just figure out which corners you wish to be raised, so if you want the north and east corner, that's tile #3 (1 + 2). The roads are organized in a similar fashion. I done it this way so that in my Isomed editor you can just draw the roads and tiles and it will use binary logic to select and combine tiles (I done something like this in my Deluxe Pacman 2 editor to draw as well).
This is an example of how these look. Believe it or not, I created these tiles just with Microsoft's Paint, that's it.