2 questions

I do because not powering up certain mons I just get bord of the game but when I power up my favorite mons I enjoy but that is why i have 10k dust but as for the abra with all those candies yes.

I am powering up my only Blissey as soon as candy arrives which is slow, 5km at a time.
I power up my high cp mons just high enough to stay awhile before getting shaved.
But I've only maxed one mon, my best dragonite.

I think powering up anything to level 30 is a safe bet. I've done this to a lot of mon. I only powered up 4 mon above 30: Dragonite (Lv 31), Gyarados 100 (Lv 36.5), Rhydon 91 (Lv 36) and Dragonite attacker (LV 31)

Even considering this, I only have 200k dust, and I only have 2 maxed mon. However, I have a plethora of level 30 mon across all types (except bug).

I recommend powering up

1. Good pokemon (I think anything above a Max CP of 2700 is a good choice)
2. Mono-type movesets for attackers. For example, I once took a Ember/Fire Blast Flareon to level 30. It is weaker than the new Fire Spin/Overheat ones, but it is by no means unusable, and still wrecks anything that doesn't resist fire.

This approach is generally good practice for gym reworks because nothing is going to be so tragically nerfed really, that makes them 'unusable'. Perhaps the only investment where I think I've regretted, is a Vileplume (RL, Petal Blizzard) and a Nidoqueen (PJ/Earthquake).

Evolve the abra he gets futuresight put dust on him he is 100 and he is so awesome. He does not learn futuresight keep it as a trophy. About the stardust power up things you like my machamp is lvl 35 why i just like machamp.

I only power up and invest stardust over level 30 on high CP gym defenders. It depends on your goals and what you want to accomplish really...I do bring some attackers to 30 like Eggs and a Venusaur so far.

To get exp, I'd evolve the 100% Abra as well, and probably as a long term side project, I'd probably evolve to Alakazam as well and power it up when I get enough dust assuming it gets the right moves...This is easy to do as you level up and probably around level 36 or so, should be able to power up any "fun" thing since levels are slow and you only need so many defenders.

Also, unlike other folks, even though I know there will be a gym rework, I just blew over 200k+ dust and maxed out on some Rhydons which can get me high gym placements...Even blowing over 300+ candies and powering up, I am still sitting on 700k+ dust and and still have enough candies to keep all my Rhydons maxed...(One was a high IV hatch)...

It's great to play conservatively so you can instantly max anything you find/hatch if you want to.

Still waiting for that useful Snorlax or Larvitar...which can also be instantly maxed as well...

Evolve but don't power him up. Will make a mean Bubblestrat Defender!