Are there any tubes I can put in my Valve Jr (head) that will induce more gain, earlier? Meaning,, going aboslutely clean (guitar -> amp head), it will start breaking up a lot earlier and maybe be stronger?

Some preamp tubes have a bit more gain, and some power tubes have less headroom (that also depends a lot on the bias) but you can't turn a valve junior into a high gain amp without SERIOUS modifications. And even with higher gain tubes it'll have too much headroom to break up at bedroom volumes.

But try asking the guys at eurotubes. I'm no expert really.
I'm not cool.
Groove Tube rates their tubes 1-10. 1 being the "dirtiest". 10 being the cleanest.
There's my way and the wrong way.
Your just not going to get a ton of gain out of a stock Vjr. With the single volume control your limited. I have 1 but it has gain and volume now and I made some changes inside to caps and resisters. It can get alot more distortion this way or clean up so I can use a distortion pedal. So tubes might make a little difference but maybe not enough. The price of the extra pot, caps and resisters is less than the price of 1 preamp tube.
You'll need to mod it or get a good distortion pedal.
Dean Icon PZ
Line 6 Variax 700
Dean V-Wing
Dean ML 79 SilverBurst
MXR M 108
H2O Chorus/Echo
Valve Junior (V3 Head/Cab and Combo)
VHT Special 6
Phonic 620 Power Pod PA
Wampler Super Plextortion
Line 6 Pod HD
put a 12at7 in and use the VJ as a clean channel it really opens up the up VJ not so boxy and the 12at7 really gets rid of alot of the hiss you hear with a 12ax7 and just sounds better imo. then add an overdrive for your gain and a eq pedal to sculpt your tone you will get some good classic rock tones maybe eq'd right some classic metal much bigger fatter and better sounding imo than using a 12ax7. and when you want to heavy it up a bit put a clean boost before your od pedal and you can get some nice metal tone's.