Ok so i am Pokemon Platinum atm and i feel unsure about certain Pokémon moves and what item to give them!

Key Note: This is before the league so keep this in mind! Also I have used up Shadow Ball for one of my team members!

Pokemon team and their movesets:

Valerian the Torterra - Lv 45
Earthquake
Woodhammer
Rockslide
Fourth move to be determined (i missed the stone edge tm in the victory road stuff so)

Raven the Staraptor (A good item for this Pokémon please) Lv.46
Aerial Ace
Roost
Fly
Close Combat

Turaya the Luxray (Might give this one magnet) - Lv.48
Thunderbolt
Crunch
Iron Tail
Thunder Fang

Hades the Houndoom - Lv.45
Flamethrower
Embargo
Thunder Fang
Dark Pulse

Wanette the Froslass - Lv.46
Ice Beam
Crunch
Psychic
Shadow Ball

Iarina the Milotic - Lv.46
Dragon Pulse
Waterfall
Surf
Safeguard

Any Item/Move suggestions for any of these would me much appreciated!!

also if this is in a wrong section your free to move it or something!!

Well, the team seems to be pretty interesting. It seems ok for me for the League, because it has nice coverage.

Being quite used to the game, I can advise you some items mainly to boost the type moves of the Pokémon. For example, miracle seed for Torterra (could be better than nothing), black glasses for Houndoom, mystic water for Milotic.
If I remember well, those items are easily obtainable. Actually, another way to go would be to use plates as well. I have collected them all in few of my gameplays, so I don't remember their positions, but I remember that the sky plate for Staraptor might be a hidden item near the League.
I think you can pretty much look up on the Internet to find the other needed plates too. I think a fire one could be pretty useful too for Houndoom. Switching between that and black galsses depending on which E4 member you're battling could be useful.
I would also recommend you to give a look at berries. There should be many in Sinnoh, so maybe there's something interesting, especially if you don't want to use too many healing items.

for a couple of move suggestions:

-Embargo's not usually all that useful since most opponents don't use items at all, and the few that do usually only use one, maybe two. That one or two items more ends up being either just a speedbump or a non-factor. So on Houndoom something like Taunt may be better to shut down any annoying non-attacking moves, like say Lucian's Mr. Mime's Reflect/Light Screen. Toxic and Will-o-Wisp are nice too.
-Froslass is a special attacker, so Crunch is not terribly good on it. Would be better on Tortetta, who has a better Attack stat.

Torterra
Curse, Leech Seed, Synthesis, Light Screen, or some other support/defensive/healing last move to help its durability, especially against physical attackers. Could have Curse + Synthesis, but that would mean sacrificing Rock Slide, and Rock is fantastic coverage on Torterra so probably not a good idea.

Staraptor
Learns Brave Bird at level 49, so you can get rid of Fly. It currently has two Flying type moves, both kinda meh for the late game. And it's missing Normal Stab, Return is an easy pick there since with max friendship you have a reliable 102 base power move. Doubt Roost would help much since Staraptor's defenses are awful and can very easily lose more than half HP in one attack. U-Turn is a great move for it since it allows an extra hit while switching to something that resist an upcoming attack.

Luxray
Physical attacker but lacks strong physical Electric move. Thunderbolt + Thunder Fang is kind of weird but sadly there isn't much you can do about that in Gen 4, Luxray's move pool is just poor.

Houndoom
Embargo seems pretty pointless since the AI very rarely use items. Nasty Plot makes Houndoom a fantastic in-game sweeper, but I guess that's not an option because it won't learn it until much later. Sunny Day + Solar Beam could work well, also boosting its Flamethrower in the process. Thunder Fang isn't great coverage, it's a weak move and Houndoom isn't even a strong physical attacker, so most of the time a Stab Dark Pulse would do more damage against Water types than a Thunder Fang, and you could also have Solar Beam to help with that.

Froslass
Crunch seems a bit redundant since if you want it to take care of Ghost and Psychic types, you already have Stab Shadow Ball for that.
Thunderbolt TM would be great coverage, but I guess you used yours on Luxray already unless you have more than one. Otherwise, maybe Thunder Wave, Light Screen, or something else for support. Rain Dance + Thunder is also an interesting combo but maybe too situational.

Milotic
Clearly a special attacker so I asume Waterfall is there just because it's an HM, should get replaced with something more useful once you no longer need it.
Ice Beam is obviously great coverage, but you probably already used yours on Froslass and Blizzard is not so reliable. Not much else you can do for it on the attacking side, but since Milotic is a great Special tank, moves like Recover and Aqua Ring may help. Seems to have nice synergy with Torterra.

Can't say much about held items because I don't recall which ones are available before the post-game. Generally Stab boosting items (like Charcoal / Black Glasses Houndoom or their equivalent Arceus Plates depending on the opponent) works fine. You can also have Lum Berries, or Sitrus Berry on the more defensive Pokémon.

These are the movesets I always use on these Pokemon whenever I have used them in Gen 4

Torterra

Solarbeam
Razor Leaf
Leaf Storm
Earthquake

Staraptor

Fly
Aerial Ace
Brave Bird
Close Combat

Luxray

Thunder
Thunder Fang
Charge Beam
Shock Wave

Houndoom

Flamethrower
Fire Fang
Dark Pulse
Sludge Bomb

Froslass

Ice Beam
Ice Fang
Shadow Ball
Dark Pulse

Milotic

Surf
Hydro Pump
Ice Beam
Recover