The energy elf(EE), is probably the most important class in MU because i gives the not so uber players the ability to play in araas they could not solo.
Now as an EE you have to relise a few things:
1:YOU CANNOT SOLO. EEs are totaly party dependant and anything an EE can solo are too low to give good exp.
2:Summons are useless, a buffed party member will always outclass your ever so slow Bali. True it can be helpful for solo but an EE should never solo anyway so let the hybrid elves have their bali's.
3:Excelent bows/crossbows are toys, an EE should be focused on keeping the party buffed and healed at all times, attacking also will just distract and EE until your partied mage dies...
Now on with the guide. First I'll discribe the armor choices.
Vine: Low reqs for low def, your armor of choice until lost tower. A +4+0 set will last till you want to go dungeon2/3 then a +4+12 set will last till lost tower. Once you are able to go LT you will want to upgrade to a higher set or if your rich upgrade to higher vine such as +7+12 preferably.
Silk:Higher reqs then vine but obviously higher def. Only upgrade to this once you enter LT, an EE under lvl 80 wearing silk will have low energy. If you cannot afford high vine this can make LT4 alot easier.
Wind:Many people say an elf using wind isn't an EE but a hybrid because of it's high reqs but I beg to differ. True the energy of a wind EE will be alot lower then a Vine EE but what use is an EE that has to pay more atention to healing itself then it's party. I use wind and no ones ever complained about my buffs. However useful wind may be in staying alive you should wait till about lvl 130-140 before upgrading to wind to give yourself decent energy. Anouther nice touch to wind is the gloves have 10 attack speed making the wind EE the fastest buffer of all.
If you want better armors go to excelent vine or silk with damage decrease or life opts but this is very expensive =/
Now training tips:
First everyone is always either saying "go all energy first" or "go str/agl for armor first" and all I have to say is either way works just fine I just prefer armor first but not at a great amount. Spend the first 10ish lvls into str/agl to wear a simple vine+4+0 set. You might say "but nobody wants to party an EE wiht no buffs", well guess what your lvl 10 can solo beatles and hunters till 15 with a kris easy then everyone and their grandma will beg you to party them in davias yeti fields.
Party at yeti fields till about lvl 30 putting all the rest of yours points into energy. You'll have all buffs and can stay at yeti fileds if you desire since everyone likes a EE however I prefer dungeon ghost room over yeti fields anyday. You can stay at ghost room till about lvl 100 if you'd like however if you like being the "exp noob" You can try bull room at lvl 40 but this will need vine+4+12 or else the thunder lichs will rape you on your way.
At this point you will have probably made lots of friends and maybe even a guild already(if not either work on your social skills or keep looking

). Try to party with people you know and trust so you get your shair of drops to upgrade your set. Keep chugging along at ghosts, yeti, or bull room until lvl 80 then the fun begins.
Now your lvl 80 and wanna go LT. First of all unless you have a very good set LT5 6 and 7(also called 8...) are off limits. If you havn't already done so find a nice guild now. Trust me there are MANY guilds that would love to have a lvl 80 EE so no prob there. If you were like me(poor..) your gonna want to upgrade your +4+x vine to +4+12 silk, this will help alot in LT4.
Now with the help of your guild you should keep training and upgrading(to wind if you can't afford higher sets) till finally you can go to LT7/8 without dying all the time. At this point just keep doing what your doing until Atlans is finally released or you quit.
basic tips:
Alway try to party both a DK and DW for the three class bonus.
Where you wanna go and where your guild wants to go are usually too diferent places so don't be afraid to buy some angels to keep yourself alive.
Make as many friends as you can.
obay the un-written law of no ksing.
set up a cd player next to your comp, buffing can get boring after so many lvls...