One way to get flight is the racial route. Be a Winged Tiefling or an Aarakocra and come online at level 1. If permanent flight isn't allowed (entirely reasonable choice for a DM) then Protector Aasimar Warlocks work too for coming online at level 1, and have proper stats for a Warlock. There are also magic items that will grant you consistent flight, since you mentioned those. And in Ravnica, the Simic Hybrid has some crazy movement tricks with Manta Glide (since falling doesn't consume your move speed, and it converts falling distance into vertical distance)
You ideally want some form of flight where you aren't concentrating on yourself, OR a really good Concentration and some sort of contingency plan for if you fall (taking falling damage + landing prone so enemies follow up with Advantage is usually bad news for you if you if you're playing at a challenging table).