To form Egypt you need admin tech 20. It is plenty of time (over 200 hundreds years or even more), so feel free to expand any direction.
Expansion in northern Italy is slow anyway.
You can try to secure egyptian land early, just wait for an opportunity to attack Mamluks.
Observe Tunis / Fezzan all the time, because this can be your path to Egypt - if you manage to get claims bordering claims on time or manage to take Sardinia / Sicily from Aragon - or by enforce peace if sth interesting happened in Maghreb..
Also note Cyprus is important here, you can fabricate directly on Mamlus from there any time you want. Cyprus will join Genoa / Venice trade leage, so you can take it for yourself by a war with any of these leages (hope it would be Genoa, they are your main rival for trade wealth anyway).
Florence is crazy reach and strong and should not have problems with securing strong allies any time. The only real problem is Pope rivalry making Florence very vulnerable to excomunication. Just make sure Papal State is never a valid rival for you and things would be OK