Budgets serve two purposes: psychological and practical.
Psychologically, it helps to quantify a goal and see progress toward that goal. The trade-off between massed and individual goals is that one looks like it’s growing more quickly (a chunk of +$10 instead of 10 lots of puny +$1s) while the other feels more tangible (generic ‘savings’ vs ‘Amazing PC / latest iPhone / glasses that work / etc’). Pick whichever way motivates you more.
Practically, the budget is your expression of your priorities. If you’re a person who prefers to accumulate money in a bucket and just buy discretionary stuff when you can afford it, go with the masses ‘savings’ - it’s much easier to keep updating. If you prefer more granularity, say, because you prioritise glasses #1 and PC/iPhone equally at #2, etc, then work out your percentage allocations for every piece of discretionary income. It can be harder to update (e.g. got $10 in birthday money, that’s $2.75 into glasses, $2 each into ...; then you recovered $3 from under the couch, so that’s $...) but you will be able to tell at a glance how much you still need for each item.
It’s horses for courses, as they say. Pick a level of detail that is useful to you, that you can sustain, and which motivates you. You have too few categories if you can’t tell how much more you need to save, and you have too many categories when you can’t stand the data entry.