Theres no large gear gap.
Getting a celestial gearset for free with 3.5 and gemming it is gonna get you to 4.5K, without any effort.
Server is barely a year old, 'meta' isn't ever gonna be 8K+ until the release of hiram.
If it takes you 6 months to reach 6K you're not playing the game right, or you simply aren't taking the game competitively enough.
I play since August 2018 and passed the 7K mark somewhen in december ?
And yes, you'll always be behind the top players because they had a 1 year advantage. Doesn't mean you cannot catch up to the point in which you can compete in pvp against them. There's only so much gearscore they can achieve. Eventually they're at the soft cap (legendary t7 gear), where they don't really gain anything anymore. So while they won't further progress, anyone can catch up.
I've donated 15euros when i started here and have been f2p ever since then. I doubt someone that donates 50euros a month cannot achieve 6K gearscore in 3months if he knows what he's doing.