Personally I hated that I couldn't upgrade my badges past bronze, but I also don't want to play with a 99 rated 77 badge player, that just isn't fun for me. This way I can pick and choose the few badges I want to give myself an edge but not be playing with some broken lovechild of Lebron and Durant on crack. Apologies if this is a re-post of existing info but I searched the internet high and low and it took me hours to eventually figure out how to get this done so I thought this post may be useful to the people of NLSC

This works on online and offline saves (would obviously recommend using on offline only) and is one of the two ways I know of to get gold badges on an offline player (the other way is to set your skill points in cheat engine to -1, which will allow you to purchase the upgrades through the menu in game where it would usually say you don't have enough points).
First off download Cheat Engine.
Make a new PG from scratch, play the tryout with whatever team you like and get to the menu where you can edit your player (later, once you have found the string that controls your badges, you can then save that string, load up other players of any position, and use it to change their badges, but you MUST start with a brand new created PG).
Then watch this video and follow each step to the letter until the point where you are adding all 77 badges:
Now, instead of changing that entire string of 00's to FF, you can simply change it one section at a time to figure out and get only the badges you want!
So we have 16 x 00 in this string, each 00 represents one group of badges and they break down as follows:
1 - Alpha Dog, Beta Dog, Closer, Cool and Collected, Fierce Competitor, Prime Time, Road Dog
2 - Defensive Anchor, Enforcer, Floor General, Heart and Soul, Mentor, Mind Games, Spark Plug, Swagger
3 - All-Time Great, Friendly, Hardened, High Work Ethic, Keep It Real, Legendary Work Ethic, Low Ego, Reserved
4 - Microwave, Unfazed, Expressive, Laid Back, Pat My Back, Unpredictable
5 - Corner Specialist, Deadeye, Limitless Range, Volume Shooter
6 - Fade Ace, Shot Creator, Lob City Finisher, Sprite Posterizer
7 - Acrobat, Hop-Stepper, King of Euros, Spin Lay-In
8 - Bank Is Open, Hustle Points, Screen Outlet, Tear Dropper
9 - Drop-Stepper, Post Hoperator, Post Spin Technician, Post Stepback Pro
10 - Dream-Like Up and Under, Killer Crossover, Spin Kingpin, Stepback Freeze
11 - Behind The Back Pro, Hesitation Stunner, Master of In and Out, Pet Move Size Up
12 - Break Starter, Flashy Passer, Lob City Passer, Pick & Roll Maestro
13 - Dimer, Scrapper, Tenacious Rebounder, Perimeter Lockdown Defender, On Court Coach
14 - Charge Card, Interceptor, Perimeter Lockdown Defender (again), Pick Dodger, Post Lockdown Defender
15 - Chase Down Artist, Eraser, Interceptor, Pick Pocket, Bruiser
16 - Brick Wall, Bruiser (again), One Man Fastbreak, Transition Finisher
Now obviously for me to figure out each exact string and what they give would take hundreds of hours and isn't possible but with a little experimentation it takes 5-10 minutes to just get the badges you want. Go to each section of the string and change the values until you get the badges you want from that particular section (I think all values 00-99 will give different results, FF gives all, F0 or 0F gives half). If you stumble upon a result that gives you the badges you want but they are bronze or silver, don't worry you can simply use the -1 skill point trick to upgrade it to where you want it.
Here's an example of my 75 rated SF that I created yesterday, I got exactly the badges I want and it took me around 5 minutes to figure it out:
00 05 00 F0 F0 F0 00 00 00 00 40 00 0F 00 00 70
Deadeye (Gold), Limitless Range (Gold), Microwave (Gold), Unfazed (Gold), Dimer (Gold), Pet Move Size Up (Bronze), Scrapper (Bronze), Lob City Finisher (Gold), One Man Fast Break (Silver), Sprite Posterizer (Gold), Transition Finisher (Gold), Mind Games, On Court Coach, Spark Plug.
This would have looked a little different at first because all of the bronze/personality badges were just earned from playing a few games, but hopefully you get the idea.
Any questions feel free to ask but I think I put pretty much all my knowledge here. GL & HF!