Lets seee here... I think I can give ya some good suggestions that haven't already been given (maybe?) lets seee...
(I'm going to have to visit some of the sites I've been visiting lately to refresh my memory.. doing research 4 you!! haha)
For Devices:
1. The Kanger Subvod! This thing is the SIZE of an ego, capable of handling sub-ohm builds. 1300mah batter (10-13 hours vape time)
2. The Innokin Endura T18 is TINY! The size of an ego battery with 1000mah (8-10 hours constant vape time) w/ very high wattage!!!
The Innokin Endura T18 is a 14-Watt REGULATED ego sized battery! That's NUTS. That means at 2ohms you'll get 5 volts of power!!
The Innokin Endura T18 is an obvious game changer in the ego size world of internal battery mods. An awesome "mod" indeed.
3. The Joyetech Ego ONE battery (and tank kit) is an awesome mod if you're willing to go a w/ a bit more girth than an ego batt.
The Ego ONE can handle 1 ohm resistance, AND its a TEMPERATURE CONTROL mod, the size of an EGO battery!! 2300 or 1100mah!!!
That means you can do 1 ohm builds and have a battery life of around 20-23 hours w/ the long version, and 9 to 11 hours w/1100mah!
4. The Eleaf iJust mod can handle 0.3 resistance coils! Thats INSAAANE for such a small tube mod!! & it's got a beefy 2600mah battery!
ALL of the above devices would be awesome choices for a first time rebuilder looking for a tiny tube style mod ^.^
Next, I'll give ya some RDA/RBT idears. (rebuildable drip atomizer, or rebuildable tank atomizer!) This'll be great!
1.) I would recommend you give a short dripping atomizer a go. How about the LowPro? It's a "low profile" RDA. U can get it for around 45 bucks, or, you can search google for a CLONE, and probably find a clone for right around 14.99-19.99 shipped!! Awesome short profile little RDA at 22mm in circumference.
2.) Next I would suggest the Derringer RDA which is another very low profile RBA dripping atomizer. Definitely a great choice.
3.) The MINI HAZE is pretty small too... definitely a popular dripping RBA. A clone can be had for less than 12 bucks I think.
All of the above RDAs are great choices for RDAs ontop of a tiny little ego style battery. Next, you should look at small profile tanks.
The KAYFUN MINI/LIGHT is 1 of the smallest little tank rebuildables you'll find, I just don't love the HEIGHT of the Kfun, but it's very popular.
The Subtank MINI is a "mini" tank (still holds a good amount of juice) and it's got a rebuilding platform.

Probably the most popular RBT tday!!
Whatever you do choose to go with, i wish you luck. You're going to have a great time. My only opinion/recommendation, is that you not limit yourself to rebuilding as your ONLY means of vaping. I made that mistake the first 6 years of my vape-career.. and it ultimately drove me away from vaping.

I definitely suggest you buy yourself some replaceable coil head tanks as-well as RDAs and RBTs... Why? Because... Rebuilding is very ZEN. It's very fun, when you WANT to rebuild. It's very meditative and relaxing when you FEEL like rebuilding... However... With a busy work-week + a family to care-for, you may find yourself in situations where... your down to your last RDA with a working wick/coil set-up. All the others are sitting in a drawer with gunky coils that just wont take another fresh cotton change... and, its 11pm on a Sunday night... Work tomorrow.. 6am sharp! and.. Your only working RDA, has funked up and gunked up for it's last time. U aint gonna be able to get a cotton thru that coil... You're gonna have-to rebuild, and all u want is sleep. So you wind-up putting it off til tomorrow night, and, at some point during the next day.. Your coil pops, and you're left without a working setup. Or, you wind-up spending 30 mins to an hour, rebuilding one of your RDAs, and you barely get 5 hours of sleep because of it. NOT cool. I def recommend always keeping a replaceable coil tank/clearomizer collection, or at-least a CE4 style clearo draw for these occasions. Just my 2 cents. Makes vaping simple.
thanks for reading. & good luck!! <3