It drove me crazy how out of date and lacking specifics the other guides are. Here is a definitive answer for those of you late to the game, but still want to know how to get this. To sum up, you'll unlock many badges pretty easily as you'll see on the list below. Once a season begins, it's broken up into weeks. At the end of each week, crew tier upgrades and player badges are given out - so check back at the end of the Rivals week and go to the Rivals Hub to trigger your achievement(s) popping.
I have not found an easy way to get directly to the badge area, but if you go to your activity feed after you earned one, you can click on that badge notification and get to the rest of the badges you've earned. Klunky, for sure.
Here is a full list of the badges - many are very easy to get:
Bronze
Getting Started -- Earn at least 4 stars on a song
Big Finish -- Nail 3 Big Rock Endings
An Alternative Path -- As a guitarist or bassist, hit at least 25 HOPOs in 5 different Alternative songs
Bassist Instinct -- As a bassist, upstrum 2,000 notes
Classic Vinyl -- Play 22 minutes of Rock, Classic Rock, or Southern Rock songs
Cranking Out the Hits -- Hit at least 250 notes while in Overdrive during a single song
Crashing the Party -- Earn at least 50,000 points in 3 different Pop-Rock songs
Energetic -- Hit at least 5 Energy Phrases in 5 different songs
Lucky -- Get a score ending in 7
Road Warrior -- Earn 25 stars in Go on Tour mode
Self-Indulgent -- As a guitarist, play a single solo that is at least 90 seconds long
Sing It Loud -- As a vocalist, earn 25 stars on songs sung by women
The Long Tail -- As a guitarist or bassist, hold a single sustained note for 5 seconds
Too Mosh of a Good Thing -- As a drummer, hit 2,000 kick drum notes while playing Punk songs
Tune Out, Drop In -- Collect 10 bars' worth of Overdrive Energy in songs from the 1960s
Block Party -- Play 30 minutes of songs from the 1970s while in multiplayer
Dropping the Hammer -- As a guitarist, hammer on or pull off 1,500 HOPO notes
Energy to Burn -- Remain in Overdrive for a total of 4 minutes on songs from the 1990s
Every Last Drop -- As a guitarist or bassist, collect 3 bars worth of Energy by whammying sustains
Face Melter -- As a guitarist, hit 1,000 notes while in Overdrive
Feeling a Connection -- Get 25 Unison Bonuses in Online Quickplay
In the Pocket -- As a bassist, upstrum at least 90% of the notes on 5 different R&B/Soul/Funk songs
Indie Darling -- Earn 5 stars on 5 different Indie Rock songs
Newly Minted -- Get 250,000 points on songs from the 2010s
Rhythm Section -- As a bassist or drummer, get at least 3 Unison Bonuses in each of 10 different songs
Serious Pipes -- Sing 250 Awesome phrases
Top Dog -- Earn 1,000 XP
Arkade of Dreams -- In Online Quickplay, get 5 stars on SOMP with a 4-player band
Helping Hand -- Save a failed bandmate 3 times
On-Camera Presence -- Deploy Overdrive 25 times in Rockudrama
Silver
Free Range -- As a guitarist, play a Great or better Freestyle solo in 5 different songs
High Flier -- As a guitarist, use the solo buttons to 100% all solos in 5 different Rock songs
Cool Cat -- Earn 2,500 XP
Leg Day -- As a drummer, hit 300 kick drum gems in a single song
Power Surge -- Hit at least 75 notes during a single Overdrive deployment
Seeing Red -- Finish a song in Brutal Mode
The -1 Club -- Play a song on Expert and miss exactly one note
Blast Beast -- As a drummer, hit at least 1,000 notes in 8 different songs
Solid Bassist -- As a bassist, get at least 90% on 8 different songs on Hard or above
Solid Drummer -- As a drummer, get at least 90% on 8 different songs on Hard or above
Solid Guitarist -- As a guitarist, get at least 90% on 8 different songs on Hard or above
Solid Vocalist -- As a vocalist, get at least 90% on 8 different songs on Hard or above
Streaker -- Get a streak of at least 500 notes in 8 different songs
Bass Gauntlet -- As a bassist, get at least 95% on 8 of these songs on Expert with the No-Fail modifier off
Guitar Gauntlet -- As a guitarist, get at least 95% on 8 of these songs on Expert with the No-Fail modifier off
Self-Possessed -- As a guitarist, get a streak of at least 666 notes in a single metal song
Vocals Gauntlet -- As a vocalist, get at least 95% on 8 of these songs on Expert with the No-Fail modifier off
From the Vault -- As a guitarist, earn 5 stars on 10 different Classic Rock songs on Expert
Gold
Flawless Bassist -- As an Expert bassist, get a Full Combo on 10 different songs
Flawless Drummer -- As an Expert drummer, get a Full Combo on 10 different songs
Flawless Vocalist -- As an Expert vocalist, get a Full Combo on 10 different songs
Flawless Guitarist -- As an Expert guitarist, get a Full Combo on 10 different songs
High Pressure -- Get a streak of at least 100 notes during a single Overdrive deployment
Plucky -- As a guitarist, score at least 250,000 points in a single song
Zeroed In -- Get a streak of at least 1,000 notes
Brutal [Instrument] -- Earn Crimson Stars on 10 different songs in Brutal mode
Superlative [Instrument] -- Get Gold Stars on 8 of the Impossible Rock Band 4 songs
Solo Career -- As an Expert guitarist, get 100% on non-freestyle solos in 10 different songs
Others
High Lonesome Sound -- Sing at least 15 Double or Triple Awesome phrases in a single Country song
House Party -- Earn 25 stars in Play a Show mode while in multiplayer
From Boston with Love -- Get 5 stars on Hard or above on the 11 The Record Co songs