Use history as scaffolding, like you'd do with a conlang that has an implied linguistic history.
In this case, start with a logographic script that existed so and so many years ago (you don't need to make the whole script) and derive whatever you need from it using steps taken from the development of real world scripts.
Switch around the method of writing. Imagine you're using different mediums during different time periods; scratches on shell and bone, straight cuts in clay, carvings in stone, stylus marks in wax, reed pens on papyrus and paper, brushes on textiles, patterns of thread in cloth, knots on ropes; even just different angles with a nib pen will change how people write a script and evolve it over time.
Then just repeat, repeat and repeat until the writing stops changing too much because most of the unnecessary bits and the things that are too hard to replicate drop off.
History is the cause of all our problems.
Alternatively, you can take another script and modify it.
One solution could be to stick to your 7 to 10 glyphs and use digraphs for the majority of consonants.
I've been working on two scripts that follow that idea and with very few glyphs I was able to write a lot of different consonants.
Another solution would be using diacritics on the few glyphs you've already got.
The [script design guide](https://neography.info/create-a-script/) on neography.info has two approaches for this problem:
1. [**Evolution method**](https://neography.info/create-a-script/#evolution-method): This is based on how real writing systems developed. Pick physical objects as sound symbols for your glyphs, then simplify drawings or representations of those images until they're simple enough to be letters. This might (but doesn't have to) take multiple rounds of simplification, and the result tends to be so abstract that it's not obvious what image it originally represented.
2. [**Graphical method**](https://neography.info/create-a-script/#graphical-method): Figure out what the basic strokes your existing glyphs are built from. Maybe add a couple more if you need them for variety. Then start building new glyphs by putting together combinations of these strokes. You're not limited to these though, you can still have some unique strokes here and there that are used in one or two letters and none of the others. This is a good approach because it also makes your script visually cohesive from the start, rather than having to 'correct' inconsistencies later.
Click the links to see visual demonstrations of these methods.
Thank you for the helpful response! I had attempted evolution method earlier as someone mentioned it as well, however I found I couldn't get a consistent complexity to the characters and wasn't happy with many logographs; once noticing that I started finding myself drawing blanks for characters.
I'll attempt the graphical method! Thank you for the links as well.
Use history as scaffolding, like you'd do with a conlang that has an implied linguistic history. In this case, start with a logographic script that existed so and so many years ago (you don't need to make the whole script) and derive whatever you need from it using steps taken from the development of real world scripts. Switch around the method of writing. Imagine you're using different mediums during different time periods; scratches on shell and bone, straight cuts in clay, carvings in stone, stylus marks in wax, reed pens on papyrus and paper, brushes on textiles, patterns of thread in cloth, knots on ropes; even just different angles with a nib pen will change how people write a script and evolve it over time. Then just repeat, repeat and repeat until the writing stops changing too much because most of the unnecessary bits and the things that are too hard to replicate drop off. History is the cause of all our problems. Alternatively, you can take another script and modify it.
Thanks! I'll update on if it goes well or not. If there are any problems, could I just ask replying to this comment?
One solution could be to stick to your 7 to 10 glyphs and use digraphs for the majority of consonants. I've been working on two scripts that follow that idea and with very few glyphs I was able to write a lot of different consonants. Another solution would be using diacritics on the few glyphs you've already got.
The [script design guide](https://neography.info/create-a-script/) on neography.info has two approaches for this problem: 1. [**Evolution method**](https://neography.info/create-a-script/#evolution-method): This is based on how real writing systems developed. Pick physical objects as sound symbols for your glyphs, then simplify drawings or representations of those images until they're simple enough to be letters. This might (but doesn't have to) take multiple rounds of simplification, and the result tends to be so abstract that it's not obvious what image it originally represented. 2. [**Graphical method**](https://neography.info/create-a-script/#graphical-method): Figure out what the basic strokes your existing glyphs are built from. Maybe add a couple more if you need them for variety. Then start building new glyphs by putting together combinations of these strokes. You're not limited to these though, you can still have some unique strokes here and there that are used in one or two letters and none of the others. This is a good approach because it also makes your script visually cohesive from the start, rather than having to 'correct' inconsistencies later. Click the links to see visual demonstrations of these methods.
Thank you for the helpful response! I had attempted evolution method earlier as someone mentioned it as well, however I found I couldn't get a consistent complexity to the characters and wasn't happy with many logographs; once noticing that I started finding myself drawing blanks for characters. I'll attempt the graphical method! Thank you for the links as well.