presale tickets for ~'s concert will go on sale very soon
tickets for ~'s concert (event/show) will be available to preorder soon.
「チケットの先行予約」= ticket presale / ticket preorder
「開始される」= go on sale / open / be available (to buy)
「もうすぐ」= soon / very soon
「もうすぐ○のチケットの先行予約が開始されるよ」= presale tickets for ~'s concert will go on sale very soon / tickets for ~'s concert (event/show) will be available to preorder soon.
「ファンクラブから順に」= fanclub members get first priority, then ..... then.....