ok i'd say you for sure need more troops. vanguards are a fast attack choice. you lack units that are effective at objective holding.

 

What would you toss around and remove to get more troops in?

 

Man really,the list is poor...very poor

Let's start by making your tactical squads in 10 men, and add some melta to you speedrs...start from there and we will see,plus the vanguard loose the heroic intervention if they have an independent caracter with them

 

Your captain lacks punch without any wargear. At least give him a power sword to take on other marines with.

Your Tac squads need fleshing out if you're to hold any objectives. They'll probably just get shot off them.

Those are really expensive landspeeders, too. You've invested over a third of your points in 6 speeders, and all they can do is wither some infantry, which your sternguard is already pretty good at. I'd lighten them up and invest in more troops and some AT. You're land raider can only shoot up one enemy tank per turn, and there's no guarantee it will take one out every turn.