Personality:

Spike is occasionally sarcastic and sometimes laughs at others' misfortunes, even though he usually means well. In Bridle Gossip, he comes up with nicknames for the ponies after their appearances change from an exposure to poison joke: Hairity, Rainbow Crash, Spitty Pie, Apple Teeny, Flutterguy, and Twilight Flopple. In Winter Wrap Up, he makes fun of Twilight's terrible nest-making and skating skills. However, he is very helpful and supportive towards Twilight in Lesson Zero. For instance, Spike is the only member of the main cast to take Twilight's concerns about missing a report to Princess Celestia seriously, unlike the others. 

Spike is a fun-loving dragon: he enjoys the welcome party that Pinkie Pie throws for Twilight in Friendship is Magic, part 1, and scarfs down candy in Luna Eclipsed.

In Owl's Well That Ends Well, he feels insecure and jealous when Twilight finds another assistant, Owlowiscious. When Fluttershy and Rainbow Dash tell Twilight about Spike's insecurity, she says, "Spike knows he can't be replaced." In Lesson Zero, Spike gets worried as Twilight becomes increasingly nervous about the due date for her friendship report. In the The Crystal Empire - Part 2, Spike and Twilight find a door enchanted by King Sombra that shows their greatest fears. Spike has a vision in which Twilight sends him away forever, scaring him.

"Looking good, Spike! Looking real good!"

Spike is often defensive about his masculinity and dismissive of things he considers "girly," although his outward disdain is often a front. In The Ticket Master, for instance, Spike scoffs at the idea of attending the "girly gala gunk" throughout the episode, but he becomes overjoyed when Princess Celestia sends him a ticket at the end. He quickly reverts to not liking it when he sees Applejack looking at him, but both laugh about it afterwards.

In Party of One, when Pinkie tells him to confess, he admits to admiring his own reflection in a mirror when nobody else is around. He does this again in The Crystalling - Part 1. In Read It and Weep, Twilight says to Rainbow Dash, "Just because you're athletic doesn't mean you aren't smart!" Spike adds, "Yeah, just look at me," curls his arm, and kisses his bicep, only to get weird looks from the mares.

Spike magically matures through his greediness in Secret of My Excess. On his birthday, Spike goes around Ponyville and requests gifts from passersby. He lets his greed get the better of him, causing him to grow into a gangly "teenager" by the next day. Zecora explains that his greed makes him grow into a monster. As he continues to grow, he develops more lizard-like qualities, such as slit pupils and a long thin-forked tongue, and his voice deepens, eventually degenerating into simple roars.

Adult Spike in Secret of My Excess.

As a massive dragon, Spike kidnaps Rarity and wreaks havoc on Ponyville. He only returns to normal when he sees Rarity wearing the fire ruby he gave her earlier in the episode, and remembers when he gave it to her. At the end of the episode, Spike concludes that he'd rather be generous, because hoarding doesn't compare to giving.

However, Spike still loves collecting and eating gems. In Just For Sidekicks, Spike agrees to take care of the ponies' pets in exchange for gems so he can bake a jewel cake. However, Spike gradually loses his gem supply throughout the day as he struggles to keep the pets in control, learning a valuable lesson in responsibility.

So try to sound exactly like him from the Show.