Np, iirc I started the same way
If you have any shot from a manga or something like that, you can just open the image and redraw the outlines with paths via pen tool. Afterwards, you hide the original image (bottom right in "Layers" tab, just click the eye on the layer to hide it), create a new layer in "Layer -> New", standard settings will do it, and name it something like "Outlines".
Then go to "Brush tool" (Hotkey: B) and use approximately these settings: "Size 3, Hardness 100%, Mode: Normal, Opacity 100%, Flow 100%".
Then make sure you have the "Outlines" Layer selected, change back to "Pen Tool", and click "Stroke Path" (Tool: Brush; Don't activate "Simulate Pressure"). This will turn the path into pixels/lines by drawing them with Brush tool on your active layer. Afterwards, you can deselet or delete the path (pressing esc or delete) as you probably won't need it anymore.
If the outlines are too thin, just increase the size of the brush in brush tool settings and draw the path again. (If you have deselected it and can't find the path again: It's next to the "Layers" tab in bottom right, there should be three tabs: Layers; Channels; Paths)
If the outlines are too massive even though you used only brush size 3, then go to "Image -> Image Size" and increase it. Then clean your Layer named Outlines and redraw the path. Even though the brush size is the same as before, it will now appear thinner as the image size is larger.*
To add colours, just add layers below the layer containing the drawn lines and use magic wand for selection of an area you want to colour (make sure that you selected "Contiguous" and "Select all Layers" in magic wand options. Usually, a sensitivity setting between 50 and 100 is fine for selection).
Then go "Selection -> Modify -> Expand" and expand it by one pixel. Afterwards, you might have to readjust the selection a little by using the Lasso Tool (you can either add or subtract parts of the previous selection by pressing shift or alt while doing a lasso selection; If you don't press either of these keys, your previous selection will disappear).
Then, just go "Edit -> Fill" after selecting the desired colour.
If you happened to have started with an original black/white image, you might have to change "Image -> Mode" to RGB first in order to use colours.
Footnote *: If you increase image size, then drawn pixels on the image will obviously blur or become unsharp. Paths however are not bound to pixels. This means even if your original file is only 400x400 and you increase it to, let's say, 4000x4000, then your paths will be as sharp as before. If you draw the path now, the resulting lines will be as sharp as ever.
So, if you draw a path on the 400x400 image file and then increase it to 4000x4000, the drawn lines will become very blurry and have a bad quality. But if you draw them from the path in 4000x4000, it will have a good quality.
I think it's just everything, taking steps over time. But I guess this is a great starter. 
