WHAT YOU'RE GOING TO NEED...
Interstellar Drive 3 or higher
Reaching the centre of the Spore galaxy is impossible without Interstellar Drive 3. And even so, that's a minimum - you need lots of health and energy packs too. Interstellar Drive 5 is vastly better. To get it you need either a Frequent Flyer 5 badge (1500 flights) or a Gopher 4 badge (40 delivery missions).
If you plan to make an alliance with the Grox, there's some special stuff you should pack:
1. Super Happy Ray
2. Planet Buster
3. 500,000 Sporebucks
4. Laser or Pulse
If you're at war when you set off for the Galactic core, chances are enemies will invade your system while you're out of the office. You may come back to find smoking ruins and a bunch of four-faced tree-lickers calling your planets home. So make sure you're at peace. This won't stop pirates attacking while you're away - and you may see some disastrous-sounding messages - but nothing too bad will happen. Pirates won't conquer your system and do anything much bar stealing a bit of spice, and even that is probably tarragon. And who's got thyme for tarragon? Certainly not us.
WHO YOU'RE GOING TO FACE...
The Grox control a massive empire that unhelpfully lies between you and the centre of the galaxy. There are only three ways to deal with it: either declare war, make an alliance with them, or just try to avoid them.
Fighting the Grox
You don't have to destroy them completely but even smashing a path through their strongholds takes considerable time. You should aim to have large stockpiles of energy and health Mega Packs plus all military upgrades, or at the very least these:
1. Extreme Energy Storage
2. Extreme Health3
3. Mega Auto Blaster
4. Mega Bomb
5. Mega Pulse
Without these you're toast. There are two ways of taking out Grox planets - bomb their colonies from low orbit with the Mega Pulse, or terraform the whole globe (making them uninhabitable for the Grox).
Is it a good idea? In a word, no. The Grox don't take kindly to it whichever method you use to destroy them, and they may even attack your homeworld - leading to a tiresome journey back to save it. And even if they don't, smashing your way through like this takes a very, very long time. Try something else.
Befriending the Grox
Do this and they'll simply leave you alone to journey to the core, but there's no such thing as a free launch - you must work hard to win them over. So make sure to pack the right stuff to get yourself in their good books. They really don't like you at first and you must tread very carefully.
It's vital you don't do anything to annoy them, so get rid of any allies with you and deactivate your Auto Blaster to avoid accidents. If you reach the hatred stage, all is lost - you'll never gain them as allies.
Burn several Extreme Energy Storage packs with the Super Happy Ray to get the 30-point max, place Embassies for 10 points and blow up neutral planets for 50 (at seven points a pop). They like that. They also like money - give them the 500,000 Sporebucks for 10 points, but don't bother donating any more as it won't help. Also, make sure to ignore the way the jerks continue to attack you even as you're being nice (they won't stop until you're allies). Don't attack them.
Once you've warmed them up from dislike to neutral, you can request missions. Save first, though. The missions tend to be either collecting artefacts, destroying other civilisations or abducting things. Sometimes this involves declaring war on other civilisations, which can cause ongoing problems for you. Other times they want you to collect artefacts from one of their own planets, which causes problems whether you do (they hate you for stealing) or don't (they dislike you for failing) do it. So just quit and reload - it's not worth the hassle. You can get 55 points for a maximum of 15 missions.