3600 i think, if all space is occupied. 7 on your opponent's + 3 your backrow + 1 your field + 1 monster (1 slot monster should be empty because you need 2 tributes)
That's not how this card works. You pay half your current LP, not 2000 LP. So if you had 4000 LP, first you would pay 2000 LP to Summon it with Masoleum of the Emperor, then you would pay 1000 LP to activate this card's effect.
Wrong cards like raigeki will power gandora up for the whole turn so if you for example if you throw out wattail dragon and use gift of the maytr then you will have gandora at 2.5k attack plus idk 5 other cards between you and your opponent annnnnd boom 4k and you can maytr away stronger cards for more attack or more than one card
But if you summon this card, by an another way.. protecting him with "Half Shut" and in your turn just turn him to attack position, he become's permanently in your monster zone. So it's a good weapon!! ;)