Seeing as there is a heavy Spec item discount this month, you're probably going to want to buy the 30 day usage periods for whatever items you're buying. Since you have 25k NX available, you probably want to buy the (1) 2 slot license so you can fit everything you want.
What items you get depends on what kind of player you are.
If you like rushing/die a lot, buy (2) first aid kits/a turret. Every death you can put more of the item and after 10+ deaths, they stack up to be an immense help in turning the tides of battle. Do note the price of the minigun turret as it was recently released and doesn't have the specialist price reduction for this month.
I'd suggest a M32 as a fun weapon to buy, because the only other time you'll be able to use it is during a Cabin Fever game, and even then you only get to play with it for 15 minutes max. It's either the (3) M32 or the Minigun, but the M32 is more noob-friendly compared to the strange recoil pattern and extreme spread of the minigun.
In my opinion, the claymore is only for shits and giggles since it requires you to camp and wait for people to pass it and for you to pull the trigger and cause it to blow them away.
The airstrikes and their cooldown timer is annoying and requires that you be constantly aware of the location of the majority of the enemy team to get any kills at all, so those are out.
Medkits/stamina kits, while helpful for you, are only good for you and yourself only, but eliminate the need to stand still and wait for health to be regenerated, one beep at a time. Use these if you're going to play a lot of elimination pro, search and destroy, or just don't want to be a team player.
The hornet is annoying and is almost as useless as the claymore because of its slow reaction speed to enemy presence and very slow dropping speed. It's akin to a turret, but has even less range and a lower chance of killing everybody but noobs. I wouldn't suggest buying it.
The incendiary launcher, while unique and "cool" is not discounted this month (according to the website) so don't waste money and buy it.
The flamethrower (also known as the "lagthrower") is not all that great unless you want to play quarantine matches all day, which I don't think most people do. I don't recommend it.
The satellite scanner is great for your team, but somewhat a waste for you yourself because you have to pull it out and play its animation that takes forever, AND have to wait for the cooldown to use it again. While others may be enjoying their momentary cham-like powers, you'll be grumbling in your camping spot waiting for the thing to recharge again.
30 day prices for Spec weapons:
2 slot - 30 days - 2900 NX
M134 Minigun - 30 days - 8900 NX
M32 Grenade Launger - 30 days - 6900 NX
First Aid Kits - 30 days - 3900 NX
Auto turret - 30 days - 8900 NX
Flamethrower - 30 days - 6900 NX
Hornet - 30 days - 3900 NX
Essentially, the ideal layout is to get the most bang for you buck. First Aid Kits are indispensable and are almost a must-have. That takes up one slot, so the other would logically be a weapon to be used with your own hands. These would be either the minigun or the M32; do note that the minigun only has 500 bullets and the grenade launcher only has 6 bullets. If not used carefully, they will run out of ammunition quickly.
Either way, no matter what you buy, as long as you only buy the items you want for 30 days, you can buy either more to swap out after a game (or before a game) to have more diversity, you can buy the 30 day items twice if you really enjoy them (60 day items :O), or the last option is to buy the items one at a time to maximize your spending and stretch your NX. If you choose to try to make the money last, I'd suggest buying a hand held weapon first for fun, and then buying some other support weapons later on to overlap.
WHEW that was a lot of typing; I wonder if it helped any xD.