Hi Adamscurr, glad to hear you're coming back to da boyz!
A lot of what I've done in recent matches is similar to what Blazinghand is doing. You can check out a bunch of battle reports posted mostly by Wyddr and I to see what I've been running to various degrees of success.
My local group has been mostly playing friendly games between 1250-1750 points. The following is kind of my base of 1250 points I start with and then kind of tweak depending on my opponent.
Bad Moons Battalion 1
HQ
Warboss w/Da KIlla Klaw, Kustom Shoota, Attack Squig (Warlord: Brutal but Kunnin')
Big Mek w/Kustom Force Field
Troops
30 Shoota Boyz w/Nob (Big Choppa)
30 Shoota Boyz w/Nob (Big Choppa)
10 Shoota Boyz
Heavy Support
15 Lootas
2 Smasha Kannons
2 Smasha Kannons
Bad Moons Battalion 2
HQ
Weirdboy (Warphead) w/ Warpath, Fists of Gork
Weirdboy w/ Da Jump
Troops
10 Gretchin
10 Gretchin
10 Gretchin
First, it's easy to make 2 battalions for extra command points with Orks. Two Weirdboy's and 30 Grots are cheap. I'll reiterate what Blazing hand said about the Gretchin; they're cheap objective holders, screeners, and bodies for the Grot Shield stratagem. The Weirdboys help with movement, mortal wounds, and buffing Da Boss and Da Boyz.
In this list I have Lootas and Smasha Gunz since I was facing Deathwatch. In my local Meta against the Ad Mech I would swap the Lootasout for Tankbustas since that player uses more vehicles. Same for Eldar Wave Serpents. Either way, max unit size is better so they can take advantage of the More Dakka and Showin' Off stratagems. Smasha Gunz are cheap, accurate for Orks, do good damage, and good at taking up space. They also have to be targeted individually when opponents shoot at them.
As for the Boyz, I like shootas for Bad Moons. 60 shots with re-rolls from the culture and auto-hits and more shots from dakka dakka dakka is pretty nice. Evil Sunz aren't a bad choice either, they don't get penalties when advancing and shooting and get bonuses to advance and charge rolls. At 1500 points and higher I take 3 full 30 Boyz units. At lower levels 1 group of 10 is nice to have for the mob up stratagem. If I have points left I'll buy Big Choppas for the Nobz. Not as good verses armor but good for multiple wound enemies.
Da Boss is a beat stick when he can get into combat. At higher levels I'll use the index Warboss on Warbike for mobility. Combining the relic klaw, brutal but kunning trait and fists of gork you have a lot of attacks, with hit and wound re-rolls, doing a lot of damage per hit. Blazinghand is right, Da Boss could take down a Knight depending on how well it rolls for saves.
The Big Mek w/ Kustom Force Field is always nice and I think I need to add a Painboy to my list to help the Boyz durability as they move.
At higher point levels I like to field a dakkajet too. Another surprisingly accurate shooting unit for Orks and helped by being Bad Moons. I one time hit 22 times on 18 shots. I then failed to wound on 21 of those hits. Good times.
So that's my basic experience and ideas on where to start. I've tried some other units here and there like Bikers, Meganobz, and Killa Kanz. Mostly they aren't tough enough, it's easy to negate their armor saves this edition, and most don't put out enough shots. The bikers can put out a lot of dakka, look cool, but wilt under fire. Trukks aren't bad either, they're more durable than before but again, still easy to negate their armor saves.