The one hairline pic you sent me from above where the hair was wet was deceptive. Looking at the hair dry it seems that your actual hairline is useable. I think you are on the right track doing two small partials, little triangles to fill in the recessed area,

And definitely keep the hair LONG while you are making this transition. Don't go getting all funky and crazy and chop it all up cause it's going to be much harder to pull off for a beginner.

For your situation what you might want to do is order a piece with the largest base size without an upcharge (9x10 maybe???) from measurements only. Send a sample of your own hair and specify that you want the piece that color all the way through.

While you are waiting for the piece, make little templates of the areas you want to fill. When the piece comes in, just cut out pieces from areas that are ventilated in the direction you want them to be for this area. For the little amount of hair you need one piece should get you several small partials. Plus, you will have extra to experiment with if you screw up once or twice.

That's what I would do. Then when you get a little experience you can start looking into expanding to fill in other areas if necessary, but then again you might be perfectly happy with the partials.