So I just bought the game and started a seasonal character but I just read that the season will be over on the 10th. Should I just wait until then to continue playing?
Wait until next season, it should start within a week or two. The new patch will come out just before the new season starts.
You don’t have enough time to complete this one.
PS: your current seasonal character will be converted to Non-Season character when season 18 ends. You’ll need to make a new seasonal character when the season 19 begins. You always start from scratch.
This is the D4 forum now… go away.
But to answer your question, you could start a seasonal character, it’ll just get transferred to a non-seasonal character on the 10th.
I think there’s a grace period between seasons though, like 2 weeks… So for 2 weeks you can play that non-seasonal character, then go make another seasonal character when the next season starts…
Either way it’s all a waste of your time if you plan on doing seasonal exclusive stuff…
You could finish the campaign, that way you get access to adventure mode next season from the start. (It’s been a while tho so not sure if you still need to complete it)
Adventure Mode is always unlocked in Seasons.
Don’t worry, seasonal character will be converted to non season so you don’t lose anything by keep playing.
You don’t need to finish campaign for adventure mode with seasonal characters, even none of your non-season characters finished campaign.
However campaign is still worth finishing if you never did.
After that:
It’ll take you a while but I recommend you to level up your first character to 70 in solo. This is your only chance to experiemce it as a new player, don’t waste it.
Do a rift and then do a Great Rift, of any tier. Finishing a GR of any tier unlocks challenge rift for you.
DON’T do challenge rift immediately; wait until season start so you seasonal character can pickup its reward.
I would suggest you continue playing your Seasonal Character in Adventure Mode. Even if you don’t get very far, it will let you get familiar with what you can expect when Season 19 starts.
When Season 18 ends and your Seasonal Character is converted to non-Season there will be 1 or 2 weeks before Season 19 begins. During this time you can play your now non-Season Character through Campaign Mode if you’re interested in following the story line. Plus it will allow you to unlock Adventure Mode in non-Season.
When the new Season starts you can stash all your and your Followers’ gear or salvage anything you don’t want to keep. With your Character and Followers completely naked you can Rebirth your Character as a Seasonal Character. You will start all over again with your Character at Level 1 and 0 Paragon Points. But, you will retain Lifetime Kills and Time Played.
Or you can just create a new Seasonal Character.
Note: If you choose to Rebirth your Character and you forget to remove their and their Followers’ gear, those items will be mailed to your non-Season. In this case, you’ll want to create a non-Season Character to collect the items from your non-Season, in-game mail. If the items are not collected within 30 days, the mail gets deleted. If you remember to remove all gear and stash it, you won’t have to worry about checking your non-Season mail.
Also note: If you have a non-Season Character that has completed Campaign Mode through Act V (killed Malthael) and unlocked Adventure Mode, do not delete that Character… ever. Doing so will cause Adventure Mode to lock again. Some players say that rebirthing a Character does the same thing.
You might also want to take a look at this Season Leveling Guide:
Good luck and good hunting! 
I’d say just play the current season so that you can play with the circles lol. When the seasons ends all your progress will be moved to non-season. You just won’t be able to complete the current season journey in less than 2 days, unless you don’t sleep or something.
Oh really? I didn’t know that
Season are prety fun, for me and many others theres nothing better than to start at 0 with friends and climb the leaderboards.
But as mentioned here season is over soon, so it’s up to you if you want to join it.
If you’re new to the game I would suggest you to play the story first, dont rush things and take your time.
Than start adventure mode, try out stuff/characters/builds in Adventure mode and so on…find the character you prefere the most.
When the season starts everyone start at 0 and you already know what char to pick for the race. 
PS: Dont do challange rift 1 week before season starts, it’s a very important resource at season start.
Here a small guide what to do at a new season: h*ttps://www.youtube.com/watch?v=JbTiESQvigA
VERY IMPORTANT: He didnt mention it in the video…as soon as you make a new season char FIRST start the game in adventure mode with the new generated season char (this way the game recognize that you made a seasonal char) and than logout and do the challange rift.
If you only create the season char but dont open a game with him, you get a cube for non season (and you dont want that).
Have fun in Diablo 3. 