Reviewing is, hands down, the best way to gather Gift Points. You will get GPs for any reviews given to a person that you have not already reviewed. Additionally, you'll get GPs for your daily review count. These are automatic.
Another way that reviewing can help with your GP fund is Auto-Reward items. These can easily be found by clicking Things To Do & Read on the left side of your screen and then clicking Auto-Reward Items. This will bring you to a list of items that automatically reward you with gift points for reviews of 250 characters or more. Your reviews of these items should ALWAYS be well over the 250 character (Note: character, not word) count! If you cannot give a quality, solid review, then you are taking advantage. Please, be thorough, honest, and kind or, in the great words of Thumper's mother, "don't say nothin' at all".
One more great way to gain gift points for reviewing is through groups. Many groups on WdC will reward you with GPs for reviews affiliated to said group or that include a multi-sig (multi-sig is an image included in a review that includes the names of several groups). I will not list any here because I don't feel that you should join groups JUST because of the reward, but for belief in the group, so you can ask me privately or seek them out through Groups or seeing the popular groups that many public reviews are affiliated with. (Yeah, bad sentence...).

Activities such as raffles and almost all WdC Contests offer a GP Prize to the winner(s). You take your chances with both and you can't be guaranteed to win, but they're fun -and contests really serve a dual-purpose because many give reviews to the entrants so that you can identify your weak points and work on strengthening your writing! Knowledge is power.

Okay, this one is a bit more confangled and less direct. Bots are games that randomly appear or are member-generated in the "Instant Message Console". (Map: Left side of screen, under where you see you name, etc... Click the rectangle icon that looks like a speech cloud from a comic book). There are several different Bot games that randomly appear:
         -Math Bot: A simple mathematical equation in written form.
         -AlphaBot: Alphabetize emoticons or Merit Badges.
         -Boxy Bot: Click random boxes until you find the one with the points.
         -Random Answer Bot: These ask a question with no definitive answer and you just kinda have to guess which random choice will be the right one.
Then, there are the three that any member may create in the IM Console (known affectionately as Scroll or Scrolls). These are:
         -G (Guessing Bot): This bot is a game of guessing the number that the member has chosen. A number that could be as low as 1 or as high as 1,000!
         -P (Puzzle Bot): Plays just like Hangman!
         -T (Trivia Bot): Question is asked and multiple answers are provided. Sometimes it makes sense, sometimes... well... not so much.

Yup. You can BUY points in the WdC Shop. $10 for 100,000GPs -and special offers and sales come around pretty often too!

Thank you! I'm so thrilled that people actually found some hint of useful information in my words! I'm delighted that you like it here at WdC! Before you know it, you'll just be calling it home --if you're not already!