The class you're looking for is the Dragonfire Adept (Dragon Magic) which provides a very respectable breath weapon (especially at high levels) "spellcasting" and some alternate forms.
You'll want to read the dragonfire adept handbook, but possible invocations involve frightful presence, interesting shapechanging, dispelling at will (which is sometimes better than SR) and all sorts of fun with dragonbreath. To save time, read through the builds here until you find one that fits your intentions.
If you want to be huge and tough:
- Dragonborn Rapotoran Cleric 4/DFA 1/Eldritch Disciple 10/Cleric 5
this provides significant cleric casting which nets you divine power (HD = BAB and a strength boost) and Righteous Might, which is a much better way of going up a size category. If you really want to tell puny mortals to cower, be a half-minotaur (LA +1 Dragon 313) or half-ogre (LA +2 dragon 313), will provide. Or start out as an anthropomorphic huge viper snake and paint your scales gold.
Instead, I'll recommend an alternate route. Since you're playing a high-level game, take cleric for your last levels, and make sure you have resources for divine metamagic and persist spell. Every day, cast divine power with persist spell and use miracle to persist giant size (wu-jen 7, castable without XP cost via miracle), Spell Resistance (It'll not be all that significant, but you'll have it), Spell Turning, Girallon's Blessing (For the claw, claw, claw, claw, rake series), and the other suite of spells. You'll be colossal and dragon-magical without needing to invest levels in a race.
Make sure your cleric has access to the hunger domain, which gives you a bite attack, and the domain spell "bite of the king" which gives you swallow whole. Unfortunately, there are no spells worth the cost that give you a tailslap or wing attacks, but your Claw Claw Claw Claw Rake Bite Swallow Whole attack sequence will simply have to make up for them.
Draconomicon (v 3.5) has the best information I have found to piece together what dragons think like and for the most part they are like geniuses that feel a small urge to eat sheep and hoard treasure.
The most important element shaping a dragon’s outlook and state of
mind is time. Dragons have no desire to live for the moment; they have
a vast supply of moments stretching out before them. They do not worry
about wasted time. If dragons have anything in excess, it is time, and
they do not concern themselves with haste. Even the dullards among
dragonkind seek to fill their time by exercising their minds. Solving
puzzles is a favorite activity, though the form these puzzles take
depends on the kind of dragon involved. Some, such as the bronze and
the copper, seek out challenging puzzles of a benign nature. Others,
such as the red and the blue, contemplate a much darker brand of
conundrums. They plot ways to satisfy their greed, to defeat
opponents, and to gain power over other creatures. Many scholars
believe that dragons owe their natural aptitude for magic to the
mental games they constantly play just to keep themselves occupied.
All true dragons have great patience. They seldom hurry or rush,
because they believe anything worth doing is worth doing right. For a
dragon, doing something right usually involves spending a long time
(from the viewpoint of shorter-lived beings) contemplating the next
step.
Are just a few examples from page 25 of the Draconomicon, seek that book for more info.
As for "what does this item make you think like" is somewhat of a different answer as noted in the comments below; the item does not turn you into a dragon with all of the ancestral memories that they would possess. Thus to answer that question "what makes someone dealing with dragons more compatible in mind set?", this would have to give you greater understanding of dragons, more then most; i.e. be closer in alignment to the dragon in question and also have great knowledge on the way said dragon would act or want. The Item does not grant all of these changes but in turn twists your mind so that you simply understand the body language of dragons innately, thus when interacting with them they seem to understand you better and as a result of this understanding you also would understand them to a much higher degree. If said dragon did not know of this item or that you possessed it, it would grant you significant advantage to social encounters with them.
I would describe to my player that while using this item, he suddenly feels everyone around him seems more blunt with their actions, their words seem so plain and open, every non-dragon seems much easier to read and I would grant them a circumstantial buff to their sense motive to any short-lived race. I do not believe they would even notice the item's influence when talking with dragons as it would feel natural.
Best Answer
The use of dragon bones is not mentioned anywhere in any official D&D 5e material. Ask your DM. Or, better yet, decide what your character would like to do with them, and ask your DM if it's possible.