Using point buy put 15 into Wisdom, take Human Variant to get Wis +1, starting is Wisdom 16 (+3), take proficiency in Perception and then a class that gives Expertise, such as 1 level of Rogue or 3 levels of Bard (giving starting proficiency of +4). Your active perception modifier is +7.
To get a higher passive perception, for your Human Variant feat take Observant, which gives +5 passive.
Next get advantage, either by having someone cast Enhance Ability - Owl's Wisdom on you or get your hands on a magic item such as Sentinel Shield, Eyes of the Eagle, Robe of Eyes, or Candle of Invocation. The highest you can roll as an active check is still 27, but you get two chances. Having advantage grants another +5 passive.
It is the combination of the Observant feat and Advantage that give the +10 boost to passive perception.
At first level a Rogue can have a passive perception of 27.
To get to 28 passive you need a +8 active modifier, which at first level will require a Wisdom of 18 either through a magic item boost such as a Tome of Understanding, or an Ioun Stone of Insight (or, if rolling ability scores a rolled 18 would give this), or wait until you can get an ability increase at level 4.
If you increase Wisdom to 18, so your active is +8, then you can get a passive of 28.
Note that a Human Variant Bard can achieve passive perception of 28 at level 4 without any magic items, as they get Expertise at level 3, and can also cast Enhance Ability on themselves.
At 5th level, your proficiency (doubled by Expertise) increases, adding another +2 to both.