What would be a good build for a beginner in this game.I read a guide that suggested a Half-Elf Fighter\Mage Multiclass and other suggest a Kensai\Mage Dual Class.
What are your thoughts and suggestion on the matter for a good and fun class for a beginner to get most out of this game and set me up nicely of BG 2 EE.Any Game play tips and advice are also appreciated.

For a first playthrough, I would advise against a Dual Class. With a Dual Class, there will be a period when your character is rather weak. Also, optimizing a dual class requires looking up experience tables and doing some math, as your experience in your first class does count against the XP cap. (If you really want to do one, I suggest dual classing early from fighter to something else, as that minimizes the down time and still gives you extra HP and equipment options.)

Also, be aware that kits (except specialist mages) and the Barbarian, Monk, and Sorcerer were not balanced with BG1 in mind.

Fighter/Mage is a decent multiclass, and it's especially nice in BG2 because there are no recruitable characters with that particular class combination. Just be aware that you can't cast mage spells while wearing armor, so you may need to use protection spells to compensate. (Fortunately, there are some really good ones like Mirror Image and Stoneskin.)

I agree with dtgreene about dualclassing. It is easy to mess up and hence was removed in later D&D versions.

Ofcourse you may play any class and it would still be fun but keep in mind that magic does not work like in other games. Low level Wizards in Baldur's Gate are extremely weak and not fun to play since they have very low hit points and little amount of spells per rest.

For a beginner the easiest classes are Fighter and Ranger. Clerics are also as good if you know how to use them.

My last playthrough was with a thief/mage. It was a blast.

I don't know about 4th and 5th editions, but 3rd edition has dual classing. It's just called "multiclassing", doesn't reset your character level and XP, and lacks the restrictions that make 1e/2e dual classing easy to mess up. (Of course, 3e multiclassing isn't without its issues, but that's another topic entirely.)

True but I wouldnt say 3rd edition multiclassing is similar to dual classing. In Dual classing you "stop" leveling in your earlier class and can never gain level in that class ever again. Also you "lose" all your first class abilities until you gain enough level in 2nd class. Both are very annoying. Well of course you already know these but I am explaining for the owner of the topic :)

Here is my build plan for Fighter\Mage Multiclass and other class ideas how is this plan or should I choose one of my other ideas

Class:Fighter/Mage
Race:Half Elf
Gender:Male
Alignment:Good

Stats

Strength 18/74 (19)
Dexterity 18 (19)
Constitution 18 (19)
Intelligence 18 (19)
Wisdom 10 (13)
Charisma 10 (11)

Starting Proficiencies

Flail:++
Two Weapon Style:++
Katana:+

Multiclass ideas

Ranger\Cleric
Fighter\Cleric


Dual Class Ideas

Fighter\Mage
Fighter\Thief
Fighter\Cleric



Single Class Ideas

Fighter
Ranger
Archer
Barbarian
Skald

From what I read if ever want to dual class I should wait play a single class in BG 1 EE then change in BG 2 EE,or just stick with single class as a human.
I am definitely going to be carrying my character onto BG 2.

What would you recommenced in terms of weapon styles and proficiency's.

Here is my planned party and party members I am interest in for BG 1

Planned Party
Imoen
Khalid
Jaheria
Minsc
Dynaheir

Interested in

Ajantis
Branwen
Coran
Kivan
Neera
Safana
Yeslick

Multi-class fighter/mage is definitely a valid build for a beginner. At low level, when you'll have very few spells, you can wear an armor most of the time, remove it only when you want to use your few spells, and at higher levels you'll have spells and magical items to compensate the lack of armor.

For Constitution, you'll only get up to 2hp bonus for the mage hp, so any point above 16 is "half-wasted". It can still be interesting, since you'll have less hp than a pure fighter and more trouble with armor, but be careful.

Else, seems fine. And your planned party is the "cannon" party (ie, BG2 assumes that was the main party), which is definitely what I would recommend for the first walkthrough.

Actually, I don't think this is the case. I am pretty sure that you do get the full hp bonus for high Constitution for all levels with rolled HP, provided that at least one of your classes is a fighter-type. (Note that this note only applies to multi classing, not dual classing.)

There's no difference between 18/51 and 18/74 strength so either go for 18/76+ or be content with 18/51+.
I recommend dumping wisdom and raising charisma instead. In you'll get cheaper shop prices and if you have 18+ cha (the friends spell can be used) you'll get better quest rewards.
Lore isn't needed since other party members will be able to identify stuff and there's also the identify spell (you can be greedy and the scroll in the prologue for learning the spell yourself instead of doing the quest).

Flail/Morningstar is a good melee weapon proficiency choice, those will get you through the game alone.
Be aware that dualwielding is a melee only style, you won't have the flexibility to switch to bow or sling with just one click (but as mage you'll have spells).

A gnome fighter/illusionist would be more powerful and fun because of the extra spells per day but not everyone likes to play a short race. For the PC I'd consider pure class Priest of Lathander or Helm. (Pure class since it's more fun than a jack of all trades.) Your planned party doesn't have access to cleric spells. Clerics can equip heavy armor and work well on the front line. Their special ability will grant them one extra attack per round temporarily.
Dualclassing isn't worth it (too many compromises) but if you want to focus more on fighting and access to druid spells multiclass ranger/cleric works too.

Actually, in 3e, if the earlier class is Paladin or Monk, you can't gain any more levels in the class after changing out of it. (Do cRPGs implement this rule?)