Yeah, echoing that. Get used to using QWER for mysteries (you will need to click the target with your mouse if you have just spoken in chat, but other than that its the easiest way.... and you can hammer keys just before the last round finishes to do a jutsu on Cooldown 1 at the start of the next round if you are really worried about getting it off in time ;).

Team 7 is the strongest starting team until you have some more ninjas. Naruto should be up front so his clones can cover other ninjas in the team to save some damage from getting through to them. Get them to 3 stars as early as possible.

Then start looking towards working on obtaining Hinata, Kiba, Tenten, Lee etc. Early game, Kiba, Lee and Tenten form a really easy to use 10-hit combo team that's good for doing nine tails events and some of the exam and instance fights where quick damage without a mystery is needed. Hinata, Neji, Shino, Ino and Shikamaru are your early game control ninjas, and working on the other Teams (8 and 10) form some easy combos, depending on your main ninja.

Don't worry too much about getting every ninja you see, but when you start unlocking adults (Kakashi, Guy, Kurenai, Asuma, Kabuto, Zabuza etc) they will be more powerful and start opening up newer tactics.

Simple early-mid game lineups:

Team 7

Lee + Kiba + Tenten (can replace Lee with Guy)

Hinata + Kurenai + Sakura/Tenten/Karin/Shizune/Asuma (really good for Wind Main)

Sasuke + Kakashi + Naruto (depending on Main)

If your server is 'Young' (meaning the average level your highest level peeps is in the 60's to early 70s) you 'can' wait till you have 10 scrolls and draw in Tendo Treasure for some useful ninja. I wouldn't waste too many coupons doing that though (maybe just buy the odd 1 or 2 to bring you up to a 10 now and then).

Lucky Board events are the best for coupon efficiency (the one with the dice rolls). Heavily Discounted Magatama are also good occasionally though you get free ones for ninja exam progress so work on that first.