Yay! Someone revived it
Anyway as for useful account upgrades. Honestly I don't think the Secret Key is worth it at the moment because there's rarely a huge selection in the backroom. You actually already have the most useful upgrade for consistently getting items and that's the Explorer Kit. I'd say about 8 times out of 10 you'll get an item which you can sell for more points.
The Amulet Coin is overall more reliable than the Itemfinder when it comes to getting more points. This is the one I'd go for first because you can start getting points faster for other things. However if you want to compete in the sitewide Shiny hunts, you're required to have a Shine Recorder which is only 6000 points.
Any other upgrades are your preference really.
Silph Scope: If you're going to be breeding a lot, the Silph Scope is a really useful one to have because it reveals your Daycare eggs.
Shelter Pass: Good because with the new clicking mechanics, you'll probably be hatching more than six eggs per day.
Bicycle: Also pretty useful if you're going to be using the Pokewalker--and in fact, the Bicycle makes it a little easier to get the Over 9000 achievement.
Lucky Egg: I bought it just for kicks, but I can't really discern how much it has helped me.
Destiny Knot: Cool, but overall not useful because breeding pairs do eventually grow to like each other (if they're interested in each other)--the Destiny Knot just makes the process faster.
Wide Lens: Again, cool, but definitely not a deal breaker to get to see one more egg in the lab than you normally would otherwise.
Odd Incense: Let's you click the same eggs/Pokemon twice. I think it's useful, but since people already hatch plenty of Pokemon as is, not sure how important it is.
Hope that was useful, and also since I don't know when you became inactive on GPX: I'd wait until GPX has sales before you buy the more expensive account upgrades because then they're 15% off. It's a bit complicated because GPX doesn't offer all the account upgrades at the same time, but it's an option.
Edit: Actually I was a little unfair to the Secret Key. You can buy summoning items (i.e the Green Orb and Rainbow Wing) from the Backroom. GPX won't allow me to see any more summoning items in the backroom because I already have plenty of them...so I'm probably not the fairest person to judge the usefulness.
. I am trying to get a shiny Kurumiru but I know thats going to be hard.
