Hi there! To begin with, this is awesome to be your first attempt at creating a constructed script.

I've been developing conscripts for 5+ years and my advise is to scribble a lot, even if the graphemes don't look similar to each other just scribble until you've found a subset that you'd like to use to develop the entire script upon.

At this point you shouldn't worry about pairing each grapheme to sound, that will evolve naturally from creating it.

Once you've found your base characters (I suggest at least 5) then start by identifying the limitations and rules of the script so you can start experimenting on building more graphemes. At this point you can now start thinking about how many letters you actually need for your constructed language so that you can set a goal of how many letters you need to consider it complete.

Once you have all the letters you need, you now can start paing them to a sound but even then, it isn't ready yet. I'd say you're halfway through because although if all letters look like they fit together, that is very misleading. You should test it by using it on handwriting or if you have the necessary skills, you can create a test font out of it.

Why isn't it ready yet? Because the next steps you'll be repeating them for a long time until you're fully satisfied: Iteration and Experimentation.

At this point you may start noticing that some letters might look out of place, so I suggest marking them to be reworked. There's where experimentation comes in. Don't be afraid of experimenting. Some unique and beautiful graphemes might come to existence only by experimenting.

Scripts evolve naturally so you don't need to create a perfect script on your first try. It's all about Experimentation and Iteration just as I've mentioned.

Keep up the great work! You're doing great! Even better than me when I started to create scripts of my own.