We can do 360’ with a few magic items and guardian of nature.

Attunement free magic items: +60'

Goggles of night (does not require attunement):

While wearing these dark lenses, you have darkvision out to a range of 60 feet. If you already have darkvision, wearing the goggles increases its range by 60 feet.

Magic items requiring attunement: +180'.

Verminshroud (EGtW, pg. 273):

you have darkvision out to a range of 60 feet. If you already have darkvision, wearing the cloak increases the range of your darkvision by 60 feet.

Robe of Eyes (does not stack with guardian of nature):

You have darkvision out to a range of 120 feet.

Wreath of the Prism (EGtW, pg. 274):

While wearing the wreath in its dormant state, you have darkvision out to a range of 60 feet. If you already have darkvision, wearing the wreath increases the range of your darkvision by 60 feet.

Color Dragon Mask (RoT):

You gain darkvision with a radius of 60 feet, or an additional 60 feet of darkvision if you already have that sense.

Silken Spite (EGtW, pg. 277):

You have darkvision out to a range of 60 feet. If you already have darkvision, being attuned to the rapier increases the range of your darkvision by 60 feet.

Orb of the Veil (EGtW, pg. 268):

You gain darkvision out to a range of 60 feet. If you already have darkvision, the orb increases its range by 60 feet.

Axe of the Dwarvish Lords (dwarves only):

The range of your darkvision increases by 60 feet.

All of these items are equivalent to an additional 60’ on top of your racial 60’, so pick goggles of night and 3 requiring attunement for a darkvision out to 300’,

Spells: 120'

We can cast the 4th level spell guardian of nature:

You gain darkvision with a range of 120 feet.

This gives +60' on top of our racial 60'

All together now: 120' (guardian of nature) + 60' (goggles of night) + 3 x 60' (3 magic items of your choice) = 360'

Honorable Mentions: The dimensional loop from Acquisitions Incorporated extends dark vision by 30'. The spell true seeing allows the caster to see up to 120' in darkness, but doesn't properly grant dark vision, so it does not interact with the items listed for the optimization part of this answer.

Seeing farther than 120 feet requires stacking different bonuses

Getting more than 120 feet of darkvision is difficult. If you had started as a dark elf it would be easy using goggles of night.

Other possibilities would be using shadow sorcerer / gloom stalker, and goggles of night. Otherwise, you have to stack magic items.

Good options

Goggles of Night and other items.

The item goggles of night gives 60 feet darkvision or increases the range by 60 feet. This would give you 120 feet.

This dndbeyond search shows more items that can increase the range of darkvision: https://www.dndbeyond.com/search?q=increases darkvision Most of these options come from the Explorer's Guide to Wildemount. The items do not specify a limit to them stacking, however, they do require attunement, so you cannot use more than three, but you can add googles of night which do not require attunement.

The spell true seeing.

The spell true seeing¹ gives 120 feet of truesight. Truesight includes seeing in normal and magic darkness.

Multiclassing.

Multiclassing one level into sorcerer you can take the shadow sorcerer (XGtE) giving 120 feet of darkvision. Multiclassing two levels of warlock is also an option to get devil's sight¹, as suggested in MivaScott's answer. The gloom stalker can also increase a racial darkvision range by 30 feet.

Bad options

Axe of the Dwarvish Lords.

The axe of the Dwarvish Lords (DMG p. 221-222) can also increase your darkvision range, but just for dwarves. Also, it is an artifact, so you won't easily come by it.

The spell darkvision.

The spell darkvision gives 60 feet of darkvision but does not increase the range, unfortunately.

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¹ Note that devil's sight and truesight do not count as darkvision. They do not, therefore interact with range increases to darkvision. On their own, they are still useful for seeing in the Underdark, however.