Welcome to the WAAAGH. Theres a lot of discussion about how to play Orks and while the general consensus is that they aren't that strong (compared to those zogging eldar, tau, necron, and spess mahreen gitz) the Orks are a fun faction to play as. Trying to win competitive games with Orks is basically playing on hard mode but its not impossibly difficult to win with Da Boyz. Figure out what your looking to get out of playing Orks and take any advise with that in mind. Somebody might say Deff Dreads absolutely terrible (and they wouldn't exactly be wrong in that assessment) but in a casual game they can be fun and potentially quite good if used well.
General tips about Orks.
Chop the shooty and shoot the choppy: Orks are a melee focused army with their shooting being generally designed to soften the enemy up to then charge in instead of it being the primarily damage dealing source. That being said Orks are not actually very good against durable melee units as Orks lack any form of defense in melee outside of armor. So the Orks generally want to get stuck into close combat against shooting focused enemies while they want to avoid close combat (until the time is right) and shoot melee focused units to wear them down. Tarpitting with lots of Boyz is often an option against really hard to kill units.
Nob with a
PK is the workhorse of a Boyz unit: To be frank boyz are not very good at killing things in melee, they have S3 base and furious charge often times isn't in effect because Orks do a lot of multi charges. The boyz rely on weight of dice rolls to drown the enemy in attacks forcing a lot of saves out of the enemy. The Nob with
PK can do the work of like 6-10 boyz in melee and its more when your up against something that's T5 or 6 with 2+ armor. That being said challenges can zog off as it puts the Nob in danger and risks the Nob getting killed before he can swing is
PK.
Always have a plan to get your Orks into the fight quickly: Shooting is the bane of Orks and marching your boyz across the table isn't going to cut the mustard. Trukks, Battlewagons, and Bikes are all valid means to transport the Orks into combat and keeps them a bit safer from being shot to death. Very few Ork units excel at long range so for most of your stuff your going to want to close the distance ASAP.
Mob Rule Sucks: Mob Rule is terrible for anything other than making giant boyz blobs impossible to sweep in melee combat. Avoid having to rely on mob rule to save your bacon as much as possible. The best Ork lists are the ones that can mitigate its existence and still keep the Orks in the fight.
And from a modeling/money saving perspective.
Kitbash, scratch build, and convert everything: Orks are the best army in the game for kitbashing and conversion work. Basically any infantry unit can be made from a Boyz or a Nobz box if you put enough effort, green stuff, and looted bits into it. Why pay $23 for a Painboy when you can make your own from a Nob box and have 4 other Nobz (or Big Meks) for basically the same price. Why buy a $45 finecast tankbusta box when you can get the much cheaper boyz box and convert them with some creative rokkit launchas (or just use the rokkit launcha that comes in each boyz kit).
As to the units you mentioned.
Boyz in trukks is Orkology 101 and probably the most bread and butter way to run boyz. Trukks explode like nobody's business and it usally kills half the squad in the process but its about numbers. One trukk is easy to stop but 10 can be a lot more difficult. Always have a Nob with
PK as mentioned above. Eavy armor is probably a worthwhile upgrade for trukk boyz.
Warbikes are one of the top tools in the Ork toolbox and list built around them are usally among the better for Orks. Forgeworld has rules for a Warboss named Zhadsnark who is incredibly good and can make bikers troops.
Buggies are dirt cheap and decent all things considered. Individual ones can be annoying for the enemy to deal with as they have to waste a units worth of firepower on a single AV10 vehicle. Very much filling that land speeder role.
Battlewagons are expensive but durable (in the front) with a decently good size transport capacity. My army lists usually revolve around Battlewagons to get my Orks into the fight (Blitz Brigade formation which is 5 Battlewagons with scout), Not the most cost effective transport but the most durable the Orks have.
Lootas are a solid choice and one of the few long range options in the Ork codex. Nothing fancy but they spam lots of S7 shots and one of the better anti air options.
Stormboyz are....... not very good

. They tend to die quickly like a boy but cost more
ppm. What they are good at is abusing
LoS blocking terrain to shield them from shooting then jump over the next turn, run
2D6 (during a WAAAGH) and charge in to create a rather large threat range. If you don't have good
LoS blocking terrain then its going to be very rough for them.
Some of the MVP units in the Ork army are
Tankbustas: Gork and Mork looked down upon the tankbustas of 5th edition, slapped them fools upside the head and said "Oi you gitz, quit mucking about and gets to krumpin dem wagonz rite proppa yer ova sized grotz". Tankbustas went from zeros to heros overnight learning how tankhunter works, realized that their tankbusta bombs are more effective when you actually pull the pin, and that you don't have to only shoot vehicles as space marines turn into a satisfying red mist when you fire a rokkit into them.
Meganobz: These lads are dead killy, durable (for an Ork), and relatively cheap in points for how hard they murder things. Throw them in a trukk, drive it at top speed at the enemy lines, force the enemy to deal with them or die horrible as massive amounts of
PK attacks rip them to shreds. Lack of Invuln saves and only T4 so don't expect miracles but they are quite good at chopping through high armor targets or assisting in chopping through an enemy unit that's being locked up by boyz.
Gretchen (grots): Those little lads are often times under appreciated but a very useful tool for the Orks. Nobody wants to waste shooting at them and they are tiny so its easy to hide them or ensure they have good cover. Can camp objectives, fill troop slots for CADs, and also act as mobile cover/screen for your boyz.
Mek Guns: Artillery is silly in that it makes your crew members act as T7 vs shooting. Grots are dirt cheap and T2 so its hilarious when scatter lasers are wounding grots on a 5+ and the artillery unit has like 20 wounds between 5 guns. The weapons themselves are a mix of good to downright laughably bad but they are generally cheap for their points and stupidly hard to shoot to death. Morale is a huge problem as grots are
Ld 5 but slap a mek in the unit and they become a "respectable" 7. Mek Gun in ruins is a major pain in the butt to deal with. Can't use them with zhadsnark sadly.