Expanding 500 points

[Bethrezen]

so right now i have a 500point space marine army consisting of

Captain - with lighting claw stormbolter

Tactical Squad - with +5 members, flamer, missile launcher

Scout Squad - with sniper rifle, camo cloaks

Assault Squad - with Power Weapon, Combat shield

i'm looking to expand this to 1000 points, i plan on taking another full Tactical Squad, and Rhinos to carry both
other than that i'm open for any suggestion on what to bring into the army

[Arlins]

sternguard are the tops, put em in a razorback and hunt MC,s . seriously great unit

[daddy4count]

Sternguard in a RB are a great choice... gives your Captain somebody to ride with.

Assault marines can be sub par in the vanilla codex... compared to other Fast choices.

Tactical squads in Rhinos are a great place to start... 2 squads with your scouts should be just about right at 1K

After that maybe some Predators or Vindicators?

[Saint]

I'd say once you satisfy the required fields of the FOC, then get one thing in each Elite, Fast Attack and Heavy. You already have fast attack. Sternguard for the Elite and a predator for heavy support would be my advice.

[Bethrezen]

would it be worth it to get terminators?

[jago668]

I would say no at 1000 points, at a base 200 points, that is a good chunk of your army.

I would add full tac squad with meltagun, missile launcher, and rhino. Then like you said another rhino for your other tactical squad. Add a 5 man sternguard with razorback, melta bomb on the sgt (just in case and had 7 points left over). Then a dakka pred (autocannon, heavy bolters).

Gives you another missile launcher, and a meltagun for armor. Sternguard have whatever you need for anti-anything-with-a-toughness-value, and the dakka pred adds in some nice fire for anything up to light armor.

[daddy4count]

pretty much that ^

[Bethrezen]

for right now the army's i'll be fighting are space wolves, grey knights, necrons, and possibly tyranids
any tips for facing them?

[mephiston_2k]

Shoot the living daylights out of them. If your buying tranports remember to buy razorback boxes as they cost the same money as a rhino kit but you get all the extra bits for the guns too.
Against Nids... heavy bolters and template weapons, general nid armour save is crap. Grey knights/Necons .. Id go with a proper predator with lascannons to deal with enemy armour or overkill elite troops/light vehicles.
Space Wolves... hard to deal with I found when played them the massed devastators are a pain in the ass, and their librarians can be nasty from a distance or up close.

[kevin]

i would recommend another troop choice and putting together a command squad to sit in a razorback with your captain. also dump the flammers for some plasma guns to increase your power. if you decide to get some sterngaurd vets anyway, buy the vets box and a 10 man vanilla squad box at the same time. the extra bits in each box will give you enough to outfit a full 10 man vet squad.