OK models you'll love to have:
Telion: he makes sniper scouts awesome. Him and Vulkan do not really mix you have better or more important units to buy.
Librarian: Vulkan is a little pricey and pushes you in one direction, however awesome that direction is.
Another rhino: land raiders can hide behind three rhinos, out of three enough will get through to do the damage.
Landspeeders: Vulkan armies tend to take speeders with Multimelta and heavy flamers.
Anyway, play
HQ
100 Librarian(give him null zone and force dome?)
Elite
205 Sternguard 4 combimeltas, plus 2 plain in a rhino(actually I would play 2 meltas, 4 plain or I like the flexibility in 2 heavy flamers and 4 combimeltas)
Troops
220 tactical squad melta(you only have a flamer :( ),
ML, combimelta (you could use a sternguard model as the serg. in this unit, though obviously this means one less combimelta for your sternguard) in a rhino.
85 Scouts 4 snipers and combimelta serg.
Heavy
145 vindi
145 vindi
That some how is a 900pt army I would not mind playing. Seriously I am surprised usually I find low point scores hard. I guess this list would be blown up at range :(, to expand to 1500 pts I could make sure to have long ranged weapons to cover this, or at least some drop poddy things to take out the long range threat
Note if you play with Vulkan all your meltas, hammers and flamers reroll to hit however they do not get combat tactics.
Combat tactics, which all the infantry in this list have, is the skill to choose to fail a morale test. This means you get charged, you die, then choose to run away, hopefully automatically recover[-this is the marine skill atgfydhgf is something like acronym, it is a bunch of words,] then your entire army shoots the offending unit. With Vulkan you will struggle to run away from combat, so you can not shoot the offending unit, this usually means you should have a powerfist in each tactical squad just in case you get charged.
Or on turn 7 you maybe shot loose a model, choose to fail morale and fall back onto an objective